I havent played the latest Stellaris or Diablo. But for all the BG/IWD/NWN games you can direct connect to an IP address. If you are on a lan it is the local/internal IP address, if its online then you use the external IP address(you normally have to forward the appropriate ports to do so). In terms of number of computers that can connect, it would be however many the game limit is. BG/IWD is 6 player limit. NWN there is no real limit per se. It is based on how fast your connection is before it starts lagging too much.
