Comment by ChocolateGod

IIRC how FiveM works now is that it pretends to be a "peer" when reusing the GTA Online protocols. Per area where players are, one player becomes the "owner" of that zone (responsible for traffic etc since there's no way for the server to know the map), it network backs to the "server peer" which in turn networks it to other players in the area. The server keeps a track of what player owns what in order to prevent cheats and sanitizes input from clients.

The server only tries to network a limited amount of players to the client (that are nearby) in order to bypass the GTA online protocol player limit. But ultimately this meant that a lot worked on FiveM compared to Alt:V (e.g. traffic, networked scenes, full character appearance etc).