Join Session as team

I’ve been approaching the multiplayer side for some time but I still have several doubts about what are the most used and best methods for managing teams.

There are so many game which allow to create a team in main menu level (Fortinite is a perfect example).

[First Question]
whether the game starts already by opening the map as with the listen and InviteOnly options, or whether another method is used.

[Second Question]
Assuming that in the main menu we have formed a team of 3 people, when looking for the lobby how can we check if there is enough space in the game for everyone to be on the same team?

let’s suppose a 5vs5 mode, how do I understand before even joining if there is space in one of the two factions, and above all, how do I communicate to the server that as soon as we enter it must assign us to that team?

Thanks for your help

The Game Session tracks num players.

Game Mode is where you organize and manage teams. Game state can have a copy of the results.