RGB monitor question

Does anybody know if standard resolution games will play on a medium resolution monitor? If they will play on a medium resolution monitor, do they look the same as if they were being played on a standard resolution monitor? The reason I ask is because I would like to be able to hook all of my stuff from my Supergun to my DC up to the same RGB monitor. I know most Saturn and Supergun games will want standard resolution, but some Saturn games and most DC games will want the higher medium resolution mode. So do I just get one Medium resolution monitor, or do I need to get a standard resoluion monitor and just continue to play my medium res games through my TV's s-video?

Also, does anybody know of a convinient switch box for selecting multiple RGB inputs to a monitor? I don't want to go switching plugs every time I play, and I have a lot of systems to hook up (SNES, Saturn, PS, DC, Supergun, Turbo grafx, N64, Cube....)