Each neighborhood is modeled by hand in external software like blender. As far as I know there is no world creator for this game. As for the backdrop, the studio spends way too much time on them seeing how they can’t be accessed and have no function other than visuals.
The prospects of a creator coming aren’t very good either. World making was a huge outlet in Sims 3, it’s hardly a coincidence they chose a design that eliminated that with the follow up game. You would think they would capitalize on it, but they can’t make a decent world to save their lives. These days, were lucky to get a dozen lots for an entire world.
