Introduced into Minecraft version 1.17.10 you now have three world upload slots! You can upload up to 3 worlds to your Minecraft Realm and they can each have different settings. Only one world can be active at a time and Realms owners can easily switch between worlds. Members would be kicked from the current world and when they rejoin are automatically placed in the new active world. Here is a walkthrough I made of the new feature to Minecraft Realms.