What operating system is suitable for Raspberry pi 3 and at the same time the size of its windows will fit into a 3.5 screen?

Question

linux

Hello. I have a Raspberry pi 3 with 3.5 screen connecting to GPIO (hdml is free) and an enclosure. Bought everything together.
The question is, what OS is suitable for the "raspberry", and at the same time the window sizes will be quietly displayed within the width of the screen? Raspbian and Ubuntu Mate are good, but they don’t want to fit on a small screen, and the screen itself doesn’t support high resolution either.
Another such moment, if you connect an external battery, will its power be enough for the board to work?

Answer 1

so the screen will not have an operating system, but one program designed for this screen.

Answer 2

About power:
It all depends on the external battery and the raspberry load. An example, if nothing hangs on the machine, then you can safely power it from the standard 1A: 5V, i.e. she is comfortable with 5W. If you hang a periphery, then it is better to take more amperes, for example 2A: 5V. When I had to hang a whistle, then 5W of the battery was enough for me, only for 15-30 minutes, and then the raspberry turned off.
Good luck!