Ah, I see now
One suggestion would to make sure that it fits 1920x1080(or any 16:9 resolution you're comfortable with) and then adjusting the screen view based on players. (3 players is always going to look silly, so you can't do much about that) so 4 players would all split up between the 1080p reso while 1 player would have that entire space, you know?
I can't get exact sizes from the images, but I'm assuming that's what you were doing XD