Skyrim is CPU-bound in cities and GPU-bound everywhere else, and the engine wastes resources on invisible objects. No Grass In Objects, eFPS, and Skyrim Priority are the free FPS wins that don't sacrifice visuals. BethINI is the config tweak that fixes stutter. These matter most on weaker GPUs, but even high-end rigs benefit from the CPU fixes.
Ranked by hand, not auto-generated. Every mod links to its full page with install guide + compatibility.