Which mods do you use to keep sims in their homeworlds?

There's a mod that I think will help you! You should check out Zer0. They have a series of mods called "Walkby" mods which prevent, for example, someone from Sulani appearing in Mount Komorebi.

[Removed by CM]

Be sure to read the specifics about the mod and make sure you download the XML injector (linked on the patreon post) if you choose to download it.