Local and Online Multiplayer?

Can the client also add new new local players? I want my game to be able to be two player split screen on two machines all playing together or four players on one machine. 3 on 1 and 1 on the other. Etc. Any configuration people want to do so there’s both online and local going on on each instance with up to 4 players on one machine or up to four players across four machines.