[N O T F || Glory]

To play custom maps yes you must download them. For mods to be implemented it depends, there are different types. Server-side mods have to be on server in order to work, there are also user mods that only you can see and use such as say a giant nade mod.

As far as rules on mods, some people use them some dont. If you add things like giant nade mods and other things some people say it takes out of the orignality of the game, totally up to you. All I know is do not use a anit recoil that is a cheat. Also custom skins are illegal in some ladders or most.