I'd like to play a save where I rotate between households that don't all live in the same world, but I'm new to using Traveler so I'd like to make sure I'm doing everything right before I start. I have a lot of questions (sorry), so I'll put them in sections.

Moving to a new homeworld
I’ve read the instructions for changing homeworld, and I’m wondering how strictly a “vacation home” is defined. When I make houses in traveler worlds “ownable”, I then get the same real estate options that I would in my homeworld. This means the option to “purchase additional home” but not “purchase vacation home” like you would see in a WA world. Does this wording matter or will an “additional” home count as a “vacation” home for the sake of changing homeworld via Traveler?

Sim-less travel between 3+ worlds
I know when sims travel to 2+ worlds on the same vacation, they need to return to all destinations in reverse order before they can return to their homeworld. Are there similar restrictions on sim-less travel? Or can I go to any number of worlds in any order as long as I don’t take anyone with me? Would travel with a sim at any point in the game affect how I would need to proceed with subsequent sim-less travel?

WA destination and Uni as homeworlds
Once a WA world or the Uni world has been activated as a homeworld, does it function any differently than a normal world as homeworld? Can sims living there have pregnancies/babies/toddlers while the world is active? If so, will those sims born there stay babies/toddlers during visits by active sims from other homeworlds or will they age up to children even if foreign aging is off? And what about role sims? I’m assuming that sims working at the WA market (relic store cashier, etc.) function the same as sims assigned to any other cashier role (elixir store cashier, etc.). Is this assumption correct? And what would happen if I made a household active that contained a sim assigned as the special merchant or professor?

Custom worlds
Is there a way, other than trial and error, to determine whether specific custom worlds are compatible with Traveler? Ideally, I’d like to include some in the rotation or as vacation spots, but I don’t want to mess anything up.

Settings for other NRAAS mods
How are settings in other NRAAS mods handled when traveling/rotating between different worlds? For example, if I want all my worlds to use the same Story Progression settings but different Tempest settings, how would I go about that? Obviously I’d need to load the Tempest settings the first time I go to each world, but would I need to reload each time or would they be remembered? Would I need to load the Story Progression settings each time I go to a new world or just in the first world I start out in?

I can answer at least some of these, and other people might jump in too.

- Moving to a new homeworld
The wording doesn't matter; just folllow the instructions (exactly) in the FAQ you found.

- Sim-less travel among 3+ worlds
It should be fine to hop from world A to world B to world C; no need to go back to your starting point. Since the sims aren't traveling, the game shouldn't be able to get confused about who lives where. Just don't do all that traveling in one play session.

- WA destination and Uni as homeworlds
According to reports I've seen, sims can have normal pregnancies and children will age normally in one of these worlds if it's a homeworld. I don't know what would happen to babies or toddlers if you traveled away and back; what I'm reading is speculation.
Role sims would function like role sims in any other world with the possible exception of the special merchant, although I'm not sure about that one. For the others, yes, they'd be like any other sim tending a cash register. If you made one active, they'd lose their role, not always right away but the assignment would be unstable.
I'd recommend having Register in play just to clean up any potential errors.

- Custom worlds
There may be a way to take the world into CAW and see whether it has a proper ID, but I've never worked with CAW and wouldn't know where to look.
Otherwise, you could test with a new save. Make one change to a homeworld like Sunset Valley, pick a random sim, travel to the custom world, and go back and see whether that change stuck. Or do it the opposite way. It doesn't need to take that long either, just enough for you to quit and reload after the first travel transition and before the second.

- Settings for other NRaas mods
In general, each new world picks up the homeworld's NRaas mod settings the first time it's simulated, and from there, the settings are distinct. So if you changed a setting in one world, it wouldn't affect any other world that you'd already visited but would be applied to any new worlds going forward.
I believe you'll be asked whether you want SP active in each new world, or at least the vacation worlds and Uni; and you'll of course need to assign manual castes if that's your thing.

puzzlezaddict post_id=88605 time=1650658796 user_id=17934 wrote: - Sim-less travel among 3+ worlds
It should be fine to hop from world A to world B to world C; no need to go back to your starting point. Since the sims aren't traveling, the game shouldn't be able to get confused about who lives where. Just don't do all that traveling in one play session.

Just to clarify this one, if I may.

When you travel with sims from World A to World B, upon landing in B the game is in vacation mode. No one is aging anywhere in this mode, pregnancies will form but not progress, among other things that are different, and the game stays that way until either Change Homeworld is invoked and the game then saved and reloaded or all traveling actively played sims return to their homeworld.

When you transition from World A to World B (travel with no sims on board), upon arrival in B you will be asked which household you would like to play/make active. The game is then not in vacation mode so there is no concept of anyone returning "home."

Thanks for the help!

I have had one issue so far. I moved some sims from World A to World B and when I traveled sim-less back to World A, the changes I made before the move were gone. I quit the game without saving, copied the World A NHD file from when I saved before going to World B, and re-did the sim-less travel. That fixed the problem. I had been using "save as" instead of "save" and changing the name of the save. My guess is that's what caused the problem - the NHD files didn't transfer to the new save file folder created by the rename. Is this the case?

No, using "save as" shouldn't be an issue. Which specific worlds are you using?