Best practices for reducing drawcalls/batches in non-linear level geometry?

I’m bouncing between large, concave sections for interiors, or just building levels out of simpler shapes, or “brushes” as they’re called in some game engine level editors. I’ve watched prototyping videos using both methods, but I’m having a hard time figuring out how to achieve fewer than 1500 batches regularly, which seems like it should be easier, given my game has a simple geometry style.

Using numerous simpler shapes seems to be better with the occlusion system, at the expense of having more objects, but I don’t know which style is more efficient for Unity’s rendering and physics system