Terrain using GPU?

I am wondering whether the Unity built-in terrain API is using specific features of the GPU especially made for terrains, or whether this is just a convenience API for using terrains. It looks to me the terrain API in Unity is pretty limited, and I am looking for a tiled terrain solution with background loading of tiles and tiles pre-loading/caching for zero wait transitions. Since I don't seem to find one, I am thinking of making one myself using meshes but I would need to know whether I would loose something in terms of GPU usage if not using the built-in terrain API. A terrain runtime engine must be able to handle height maps, texture splatting, collisions and mipmaps.