Does it matter what level you set the difficulty as at the start of the game? I see some people leave it at 2 and others put it at 0 or 4.

Hi, welcome in! The difficulty level affects how much time you're given, but because we're holding 2 all the way through, it's literally only one frame per level per diffculty step. So to go from 0 to 1 saves 6 frames, etc.