Let's say I Get a 2 player realm and I send an invite to 5 friends, let's call them a, b, c, d and e. I want all 5 to play therefore is it possible for a and b to play then b logs off and d plays. Basically can 5 people have access to the realm but only 2 can play it at a time.
There can be an infinite quantity of players able to join the realm, there can be an infinite quantity of invites out at a single time.
However, a realm can only have 3 concurrent players, 2 non-owners and one slot reserved for the owner only.
Let's say you were the owner, you invite 20 players to the realm, all 20 can accept, and let's say they do.
Only two of your friends can be playing at a time, the other 18 will be unable to join, you, on the other hand, have one slot reserved for yourself.
You can have an infinite quantity of players ABLE to join, but only two can PLAY at a time.