Yes
Each connectiong will recieve the messages for the rooms that that connection has JOINed
So
Connection 1 in rooms foo and bar
Connection 2 in rooms cake and pie
Connection 3 in rooms cake and lemon
Connection 2 will not recieved messages from foo and bar.
Connection 2 and 3 will recieved messages for cake as both connections are in cake
Connection 3 will get lemon but not pie.
So
Yes.
Then it’s just down to what the server can handle in terms of traffic not just the given process keeping up.
Broadly speaking:
Rate limit is by “IP” so you have a shared rate limit across all the connections from the same server, broadly speaking.
Discussing rate limit can get complicated very quickly.