I think your last questions illustrate why I chose to carry and recommend the Ultimachine boards over the imports even though they have a higher cost. (plus digipots)
I make CNC based machines. Printers, sand tables, Routers, they are all tools that have a learning curve. All your questions are electronics based. If I felt those boards were easier or better I would recommend them. For the price difference do you want to tweak settings and diagnose issues or would your rather use and learn your machine. We spent the better part of two years diagnosing crappy board issues that were ever changing, components got worse and worse. Since switching to high quality boards we have leapfrogged in machine performance because we are not spending 80% of our time trying to figure out why things are not working. We went from wood to steel milling. With your money you need to choose where you want to spend your time, whatever you chose has no effect on our opinion of you.
All that said, you could buy a $5 board and have it actually work, it is very much like a lottery. I really do understand your side, I hate spending this kind of money unless it is justified, I would love to lower the overall cost of my machines, I would sell more and that in turn leads to more profit. I am now quality over quantity, because I enjoy working with my tools not trying to fix them So I make a bundle that I believe is the easiest/best path to a successful and fun build. For the super DIY type, they can use my parts list and make changes as they see fit.
Some people here love testing out new products and boards and problem solving, other people just want to make stuff. Both are welcome (I go back and forth every few months) but you would be best to choose what you prefer to do.