I am about to tackle the problem of players having different screen resolutions. is there any advice you can give me?
Python:
bge.render.setWindowSize(x,y)
If you want fullscreen:
bge.render.setFullScreen(enable)
Bear in mind there are different fullscreen modes, allowing letterbox (black bars if screen res doesn’t match), scale, or stretch.
As for how you manage all that, I’m afraid it’s quite hard.