Shadows and lighting are the biggest in FPS drops in Skyrim. I remember once that I made it so shadows were FXAA only, and radius of 1 so that the shadows only were on stuff that needed shadows (this included land shadows.) For instance, it would show a little blurry shadow circle under NPCs and the player based on the shape of the NPC / player and how they are walking / running. I don't remember how to do this, and it's possible the nexus page for it was deleted. It was the best shadow implementation for low-performance.
Dead Space 3 now that I've got my layered textures fixed: