Love2Design

Photo and Designer share many features so there is not going to be much difference. Both can load the files you mention (apart from native .procreate). Your biggest issue is likely to be converting things like text or gradients. All of which can sometimes be an issue, so it will depend on what is in the Procreate files.
I think Designer would be ideal and expect .psd or PDF would be the best choice for file format.

Hi Love2Design,
What format are the files in as Affinity can't open procreate files.
Thanks
Callum

I expect it’s a “lost in translation” thing.
Printers use CMYK as the basic inks because mixing them gives you most colours from inks. Mixing RGB inks just would not work, as I said, you cannot get yellow.
What they might mean is that their printer has additional inks, as well as CMYK. It is not uncommon for printers to have 6 or more colours to increase the range of colours they can print. I have a Canon inkjet printer that has 8 inks. As well as CMYK, it has red, green and a lighter ‘photo’ version of Cyan and of Magenta (for subtle toning). The red and green inks really help because oranges and greens especially, are very hard to produce with CMYK. The green ink is obvious and the red mixes very well with yellow to make orange.
That would explain why they use an RGB workflow. The wider colour range of RGB can be translated into CMYK+RG (might be more colours) to give a much wider printable range. If your image has already been converted to CMYK the extra colours of RGB have gone forever. 
For that, calibrating your monitor and using Soft proofing layers should be ideal. 

Today's monitors still degrade through time ? I've always heard is good to re-calibrate from time to time, ie, once a month... Maybe I'm doing stupid extra work, lol...
One question (you see to be very well versed in color managment and print.. I only nerded in what I needed for my illustration and graphic design (initially was mostly for web) works...):
Would you see it terrible to use a CMYK samples book instead ? I purchased that quite cheap in amazon (4 or 5 times cheaper than the cheapest pantone book, and I mean those only containing a few colors). You know, these that have grids of mixes in percentages (10%, 20%, 30%...) ...it quite served for me to get good enough accuracy for my gigs... of course, way far from a photo lab or very serious printing stuff... I mean, I was even getting wrong reds before, on-screen... after calibrating by hardware carefully, and using this book in the process, comparing to screen, neutral (6500) lighting, etc, it ended accurate enough, as I have other tricks to ensure the thing keeps reasonable. Probably is also my type of small business owners, other indies, other individuals "clients", which till date have never found an issue with color accuracy...  Probably is a terrible method, but again, depend on the target users, i guess....
From X-Rite, i1 Display Pro works great for me. Over a NEC Spectraview (a NEC produced in Europe that used to get calibration from default, which I calibrated on my own, and do so often. Didn't have the bucks for an Eizo, this one was already expensive, sigh....).
To my continued surprise, a lot of the print companies with which these small business owners and all sort of individuals use,  they tend to use some sort of RGB based workflow. Or probably, that they know their users have often even less clues than me about color management, and know that all they are going to get is a PNG or bad JPG.... I have found a bunch of them stating in the docs that they don't accept CMYK files !  I typically ask the project author where do they intend to print (the pain is when they do decide that at the very end of the project, as they plan to hunt for the cheapest printing deal) , so I check the online POD printing company docs, some hide it stupidly well, and in some cases, they don't have that, so I ask the person to forward my exact questions to them. Usually is very well documented. What CMYK profile they want, which level of ink, or if they want just sRGB based files (very frequent), resolution, they typically even provide templates in several formats, already with their bleed, cutting guides, etc. In general a cmyk file with the profile they needs is wat gets more accuracy, but at times is the opposite. With a few I just have seen that the best is provide a good sRGB file (anyway, I control that no tones get out of range of the usual CMYK profiles).
I ain't no color expert as a few of you are... I just nerded on the matter per need, as usual.... More of a graphic game artist and illustrator who had to work a lot of years as graphic designer, but print was one of the things to do, only.... But I can speak of some tricks that at least for my requested outputs seem to work pretty well....
The laptops , at least PC based, which are the ones I know, tend to be pretty bad in Adobe RGB color space support. And have typically more issues. Older ones indeed used to be only TN panels, and those are the worst for color accuracy (with some rare exceptions), also because degrade the image colors per angle a lot more, some require that u have your head fully straight over it, not even in a slight angle. If is an IPS or VA panel, that's a lot of a better case, being IPS generally safer (VA generally very good for contrast, deep blacks and subtle "whites" ). So... I think u can use a laptop, but I'd definitely get an external monitor. Pity is that most semi professional (and professional ones) monitors tend to be pretty heavy, among other things for having a more solid support, capable of many more positions, etc. So, kills the portable matter, BUT, if you get one, and do calibrate the best u can the laptop screen, you could still carry it for work for lines-only stuff, sketches, non graphic work, knowing , surely with time where and how color aberrations happen... as you would often compare the two screens. They also tend to suffer from light leaks in the outer areas, and lighting uniformity issues, which is horrid as will display colors differently on screen depending on the area. Usually a good semi-professional monitor has all these things sort of minimized.
Personally, I prefer even for the constant moving situation, unless if it is carry the laptop everyday from hoe to work, if is only that you move every x months, I prefer just a powerful machine, but a mini-tower, can be very lightweight, I used to carry in latest company one under my arm in the bus when every x months I needed to "build my seat" at the company, as latest years I became a remote worker. U know, sometimes even these have to work in-site. I can imagine that for someone who moves from time to time, can put the mini tower in the back of the car, no biggie (some ppl might remember my every week-end travel anecdote with a large CRT there).
Latest years my workflow is very specific, I often just work in sRGB. But in the past, specially working at a company where I made all print material for it, no online printing companies, I used to work in RGB and then convert to CMYK to the needed profile at the end, but with several checks in the middle. OR... working in CMYK mode from start. That was typically with a PS CS2, during many years. I used to carry the stuff to the print company my self, and do some test prints there, to ensure everything... no big issues.... Even if the process was extremely far from perfect.
 

You can NEVER set the screen colours to CMYK. Monitors use Red Green and Blue light and RGB light can display far more colours than CMYK can print
Basically, the calibration device will only make your screen display accurate RGB colours. It’s the Soft proof layer that will make the Affinity RGB image look closer to CMYK.
You can’t download an ICC profile for your screen. The calibrator has to actually “see” your screen. It’s like me saying your screen is too bright. How would I know ? . 
Any device should be fine, Spyder , Munki or X-rite. I have a Spyder, so can’t comment personally on the others.
If you set the Pantone colours in Affinity, using the CMYK Pantone Swatches in the swatches panel, you will then be using the physical Pantone swatch to see what those colours will actually print like. The print colours will/should look like the physical swatch  colours. It doesn’t matter what they look like on the screen so you don’t need a Soft proof layer for that. Just do it by numbers.
Why would you want to turn it off? You are looking at the actual colours of the image, not some unrealistic overbright, too red distorted image. OK, maybe I have seen your monitor . You only use soft proof layers to visualise what RGB colours will look like when printed to CMYK. Normally, your calibrated monitor will just display accurate RGB colours and you won’t be using Soft proof layers when editing photographs, I hope 
 

If not convenient for now, buy a laptop but try and get one where the screen display does not appear to change too much as you alter the viewing angle. That will probably do you for a while but be careful how you view it (as I described earlier).
Use a calibration device on it!!!
With the RGB workflow printer, get your proofs made and use a soft proof to match the display to the proof (more or less).
If you are designing in CMYK for the CMYK workflow printer, I would recommend that you use a different approach and buy a Pantone CMYK swatch. Not a ‘normal’ Pantone colour swatch. You need the uncoated part, because obviously materials are not coated.
https://www.pantone.com/color-bridge-coated-uncoated
That will show you what CMYK colours should look like when you use them. Then it’s up to the printer company to match them. Don’t try to do it visually on the monitor, that’s too much like hard work  Literally, ‘print by numbers’.
Design a test page in CMYK using the swatch colours and get that printed but talk to the printers first so they know what you are after and ask for advice. Especially about using Pantone colours etc. They will know best.
A CMYK swatch is interesting because it’s amazing how it shows the limitations of using just cyan, magenta and yellow inks with some colours.
Good luck

Well, now I know the process, it makes it easier for me, but harder for you  Forget what I said about Pantone spot colours, that won't happen with the Direct to Garment process.
Absolutely the first thing you need to do is sort out your viewing. I am not a fan of using laptops because the displays are not really designed for colour accuracy and the colours you see on screen can change depending on viewing angle and ambient lighting.  
However, assuming you don't want to buy a new computer and monitor just yet, you must calibrate what you have, Buy a Spyder (or similar)  calibration device  https://www.datacolor.com/photography-design/product-overview/spyder5-family/ they are not expensive and you can use it on any computer.
After calibrating, make sure that you always view your laptop at the same angle and under similar ambient lighting conditions. Obviously, you can design anywhere, but view the colours where you can assess them properly. (and consistently). Make sure that the laptop is always plugged in to the mains as most dim the display to save batteries when not plugged in.
Because of the type of printing process, you will need to do some work. First thing is to design a calibration page. Something with a stock photo and a range of colours on it.
Something like this from Adobe.

or use that, search for Adobe Calibration Image.
Get that printed by the different printers as a sample (ideally on a couple of different items as colours will vary a bit between materials). Now you will need to see how the print compares to the 'calibration image' on your newly calibrated screen 
If it is 'off colour', this is where Affinity's Soft Proofing might come in handy. See if any of the preset profiles get the colour close .Under no circumstance adjust your calibrated screen !!!
Design something you like, apply the soft proof layer temporarily and that should be pretty much what you will get. Some colours just wont look good, like oranges and greens because CMYK can't reproduce them. It is all about being able to design something that can be printed! Not the other way round.
Remember that the soft proof layer is only there to temporarily adjust you monitor for viewing. Make sure you delete it or turn it off before sending your design to be printed or it will mess up the whole process.
That's the best place to start.
 

Matching colours is such a tough subject. Made 10 times worse when you are printing on fabrics.
I spent a lot of time trying to do this for litho and silkscreen printing and it never works that well.
I must admit I don't know anything about printing on things like pillows but know something about tee-shirts, as long as you are talking about four-colour process and trying to match colours is very tough. The biggest problem is dot gain, which is where the dots of the printing enlarges when printed. This is a big problem on material, as ink soaks in and spreads. If you have ever spilt something on a new tee-shirt, you will be very familiar with the process . That is where using the correct printer profiles comes in.
Another problem is that the "white" of the fabric varies.
The last thing you want for matching is a computer that displays lots of RGB colours. Because no matter what is displays, the printer can't print. Printers use three colours plus black and can print only a fraction of normal RGB, let alone Adobe "full" RGB.
What you need is a monitor that is calibrated. Using something like a Spyder colour calibration device, it will try and match what you see to what you print. That will mean making your display look dull and muddy, because that is what your print will be.
Pretty much any computer screen can display CMYK colours but the screen will need to be calibrated. That means a proper monitor, a calibration device and proper software. So forget laptop screens and especially, forget iPads. Even then, I'm not sure how well this will work when printing on fabrics, but it will be a damn sight better than using an iPad.
However, what are you printing?
Are you trying to match something like a photo, or creating patterns.
If you are printing patterns, then I would normally expect that to be done using spot colours so that whatever colour you want can be printed, just make sure you select the "u" (uncoated) colours, not "c" (coated) colours. Choose a colour from a swatch (Pantone) then you printer can match that because that is the colour of the ink. Trying to match it on the computer does not apply. Just design using spot colours from the swatch but again, forget iPad because Affinity Designer does not support creating in spot colours.
Unless there is something physically wrong with you Mac, you would be better off to buy a separate monitor and a calibration device. I am not sure how this works with Macs but it works on a PC laptop.
Or, if practical buy a Pantone swatch and use spot colours instead.

While i can't comment on the choice of laptop, i've not kept up to speed with Windows laptops since i switched to Macs a few years back.  I have the 9.7 iPad Pro, which i find has a big enough screen for photo editing BUT can see how a bigger screen would benefit Designer, as you'd have more of an area to draw/paint with.  As for iPad storage, i'd say the more the better as .afphoto and .afdesign files can be large.  From looking online, you can connect a USB hard to an iPad with an adaptor, it's not something i've done before and hopefully if someone else has, they will comment here