The ExtremeOT Optinal-PVP system works like this:
If you are in a Guild, you will automatically be at War against all other Guilds, that is, If you are in a Guild and kill another player who is in a Guild, FRAG does not count for the Red Skull or Ban system.
If you are in a Guild you can not kill a Player WITHOUT Guild and the Player WITHOUT Guild kill can not attack a player who is in a Guild.
When joining a guild, the player will have a cooldown of 24 hours to be able to leave his guild, that is, if you join a guild and, 10 minutes later try to leave it you will not be able to. Only just after 24 hours.
if you try to pass guild leadership to other player, it will receive a 24 hours cooldown too. If you leave a guild, you will be able to join in another one just after 24 hours.
Basically PVP will be enabled when both players are in a guild and there will no longer be unjustified kills on the server.
All Players who are in Guild gain 10% more EXP.