Having a game with couch co-op, how many players can remotely play together?
In this case, only one player has the PS4 in front of them. Another can join via PS Remote Play for sure. But can a 3rd and 4th player do that as well?
Sadly, there is a limit of one Remote Play connection per console. In other words, if one player is connected via PS Remote Play (or any 3rd party Remote Play implementations like Chiaki), the rest will be unable to join and will get an error message instead.