You don’t need to sculpt anything, if you already have a heightmap (which you would need to use tessellation) then you can just subdivide a mesh and apply the heightmap as a displacement map and export it. It’s not as convenient, but you’ll get nicer results than you can currently get with regular tessellation.
I am hoping Epic will add a tessellate/displace option to the geometry modeling tools in engine, so that this doesn’t require constantly switching programs in the future. The modeling tools are improving fairly rapidly, as evidenced by the fact that the latest quixel scene’s building meshes were constructed mostly within UE4 using scan data.