30 fps is fine if the city actually works
I would take a dense city running at a stable 30 over a 60 fps mode that empties the sidewalks, cuts traffic and turns every interior into a locked texture.
People act like 30 fps is a human rights violation. It is not ideal. It is also not the only thing a giant simulation is doing.
Give me crowds that react, stores with actual spaces behind the doors, traffic that does not disappear when I turn around, and a hotel where the elevator works. If that costs frames, take the frames.
A performance mode would be great. But if the choice is visual smoothness or a city that feels occupied, I am choosing the city.