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Makes perfect sense. We have these awesome tools at our disposal—it's up to us to learn them and be flexible with their quirks.

Glad it was helpful. It gets a lot more intuitive the more you become familiar with the interface and various tools.
Every software vendor has their own interface, tools, usages, techniques, strengths and weaknesses. We just have to get used to a new way of doing things to take advantage of each software's "idiosyncrasies". I was an Adobe user since 1995. When first switching to Affinity, I "wanted" the new software to work the way I was used to working, using the tools that worked in my old software. I like some things much better in Affinity, and some not as much. Same with Adobe though. 😏
I often use the Pen tool for exact lines and curves, so I like that it defaults to a thin line. A complex curve applied when using the Pen could get in the way of precision. 
You can also copy and paste a style from one curve or object to another, or use the Style Picker tool. Lots of ways to do things. 

Thank you for taking the time to help, Ldina. I appreciate your help.
What really helped in your post was when you said, "After you have at least two nodes created (with you pen tool and your curve still active), click on whichever brush you wish to use." I was trying to set the brush before plotting any nodes, which does not work. When I set the brush afterwards, it defaults to the size set in the particular brush. That was my other issue resolved. I needed to edit the brush settings and lessen the size, so when I chose that brush, it wouldn't be gigantic.
I figured out the problem with my corners not joining properly. I just saw your response about the miter settings, which I tried earlier without success. In the end, it turned out to be an overlook on my part. In the iPad brush studio, there are Pencils that are specifically for closed curves, as stated in parenthesis. When I use one of those pencils, the corners are solid and joined properly.
I just have to get used to the Pen tool always defaulting to a solid line, and not a custom brush. I think I can go forward now and get used to this workflow.
 

With the pen tool selected, if you click on the stroke size in the context menu, one of the options you should see in the dialog is "Cap". Choose the square-ended one.