If you want to remove the total number of players go to Map>Player Properties, under the player tab, change controller to "None".
If you just want to adjust team sizes, but not overall players go to Map>Game Variants. Here you can adjust the different play options. If you don't want the default ones, uncheck the box in the bottom left, then add your own. You can adjust the max team size and other options here.
This can also be done in Game Variants. Under player attributes tab, there's a box called Hidden Attributes. Checking them will hide those for all players. You can also lock/unlock these values on a per player basis by clicking on the player, and scrolling to the relevant attribute.