Most efficient way for 3D tiles?

I'm looking for a way to quickly build worlds like with the 2D tilemap, e.g. make a few 3D objects in Blender and import them into Unity.
Anything wrong with just using the 2D tilemap and use the prefab brush? In the official 2D prefab brush video it is used to paint 3D trees on top of a plane.

Is there a better (easier and/or more performant) way to build a 3D world with tiles? I've looked into the terrain tool, but it seems overkill and I'm actually looking for a much simpler style.

I've only used planes before to create 3D worlds, or space games.... what I am looking for specifically now is making a grass land that has rivers, the rivers should be somewhat lower and the shoretiles angled (leading into the water).

Thanks!