I want to have an AI or multiplayer game with say X amount of players, preferably over 20. Can anyone help me out?
The player caps are server enforced. In order to host a game with 11+ player slots and/or 4+ spec slots (There is no hardcoded limit on either category AFAIK so 100+ players and specs is possible, although a bad idea) you need to host a PAStats Custom Server. This guide should help you out: http://exodusesports.com/guides/planetary-annihilation-dedicated-server-setup/ You'd also want to set up a modded server on vanilla that redirects to the custom server so that players without PAStats could join. I think you'll have to ask @cola_colin and @mikeyh about that.
Yes. And you can modify your local server files to allow for more players. Planetary Annihilation/stable/media/server-script/states/lobby. There is a MAX_PLAYERS in there. Change it.
Is there also a mod to make a single giant planet that I currently can't make with the limitations? I used to play total annihilation and while I love the multi planet fighting I really want a super huge planet that won't crash my system. The only thing missing is the krogoth. Dang. Maybe there is a mod for that.
You can use DirectEdit to make planets arbitrarily large or small, but really big planets tend to take ages to load.
I like taking things to the extreme so I was gonna make the planet crazy big. The texture would probably be messed up though. Maybe there's a way to mitigate this.