depending on how good your terrain material is, you can use just terrain for distant cliffs, but I don’t think terrain can ever look good enough w/o the help of a SM for close to a player. Unless you go bananas with SM’s it will be fairly cheap in regards to cpu/gpu/drawcalls (if draw calls are an issue you can put all the meshes into the veg tool to combine them to 1 draw call) the terrain is optimized for large distances so that would be ideal, but then again if your SM have LOD’s you can use them everywhere, almost care free.