As written before, you can connect 4 directly via LAN. Of course, even more are possible via a switch. Just as with WLAN. As many participants are possible as there are IP addresses available. Whether the router can handle that many is questionable. But with 10-15 participants it is no problem

LAN 4x, WLAN theoretically unlimited, but the router is pretty weak on the chest. It's probably not much fun with more than 10 concurrent devices.