With full screen, I see a lot of Steam discussion about "game is just a black screen" because their monitor can't handle full screen. So I don't recommend starting in full screen. Not only that, but using cloud to keep a full screen setting, might not be good, because people get new computers that might not work well with full screen.
If you do upscale, I highly recommend increments of 50%. Keeps it from looking awful, or stretched.
Viewing post in Do you play in Fullscreen or Windowed?
That's a good point, aspect ratio is not a problem, but when scaling up I will provide a option for how you want me to scale it up:
"Nearest" will just stretch without filtering, it may result clearer image in best case and in pixelated results in worst case scenario
"Linear" will do a linear interpolation when scaling, it may result in smoother imager in best case and it blurrier in worst case scenario