It would vastly depend on the game.
if you are racing in the streets, then buildings with multiple LODs are a prerequisite. They just cannot pop at all or they destroy the feel of the game.
you may be able to get away with only using impostors if you have a MonteCarlo type race, where the buildings are separated form the tarmac.
if you have a large enough map sectoring and streaming may help, but ultimately, if the speed and size is right, a single map may be best for player experience.
Personally, I think those are all determinations I would make after the alpha is done with, based on the lowest tear PC or whatever I’m interested in supporting.
Afterall, there are tons of tricks one can employ later on, like converting the whole landscape to static meshes and gain a ton of performance…