You should be able to join any world on a realm

You should be able to pick which world you want to join on a realm, so for example, 2 players on World 1, 5 players on World 2, and 3 players on World 3 (no max player count on each world, only limit is how many can be on the realm), and the realm owner should be able to pick a world that could only be played by the owner, only played by the administrators (for bedrock), or played by everyone (the default)