Wacom MobileStudio Pro 16

[ZenosArt]

My problem is with the Affinity designer once I try to paint directly on the screen with the pen. 

The screen starts to flicker each time I come closer to the screen with the pen and try to draw. 

The problem is not related to my device since the same procedure works fine with photoshop. 

I have Affinity V2 suite. Win 10 has been updated to the last version. 

[SrPx]

Yes, these apps need the system to be very up to date (specially the graphics driver and Windows Updates) and curated, so to speak (which is an advantage in the long run, tho). I would uninstall the graphic card driver, reboot, install the newest version of the driver for your graphic card on  the card's website. (and then reboot before starting Designer again). Even if in Photoshop it does work well, as yep, it also uses a bit the GPU for the brushes, but I think in a different way, internally. BUT... I'd try FIRST the below steps :

In Designer's Preferences. In "Performance" , disable 'Hardware acceleration - Open CL' and in Retina Render , set "Auto".  In "View Quality" set "Bilineal (best quality".

In Preferences->Tools-> Tablet Input set "Windows Ink".

In Preferences-> User Interface , make sure "Show lines as points" is CHECKED (this is for other issues, it's a temporary fix, once fixed you might want to uncheck it (or not)), and "pointer support" is NOT checked. As that one brings back certain graphic annoyances from Windows Pen and Ink service.

Beware, setting "Windows Ink" in Affinity Preferences requires that in your Wacom panel (outside Affinity) you need to set the application profile you surely have created (you should, imo) for Designer, in its "Mapping" tab "Windows Ink" as checked, marked. Also, while you are there, IF you have two or more monitors, make very sure you have selected in "Screen Area" the main screen for your editing apps (ie, 'Monitor 1'). Otherwise Wacom will be considering the full 2 screens' space, causing many problems. Be sure to also check "force proportions" (or something like that), as it ensures your lines and brush strokes keep same proportion to what you draw in screen. Otherwise you lose accuracy.

It could be also an issue with the screen-pen calibration.  Do you have set Windows Scaling (in Windows Settings->System-> Screen, this is out of Affinity) some "custom scaling" ? Or do you have it at 100% or 125% ? Try changing that as well, maybe this could be causing some problem (again, even if in Photoshop there's no problem). You can use custom settings for Windows Scaling, by typing a number, after clicking the advanced/custom option, it works well with Affinity, and in my experience, some factors/numbers might give a problem, so it's imo good to try others.

The mentioned settings work great for me in Designer (and all Affinity apps, as the internals seem to be similar for this), yet though, I have an old Wacom Intuos pro 4 XL (Cintiqs and Mobile Studios can have more problems due to the screen-pen calibration and etc).