I can only go on what i have seen myself - there are too many combinations, but the ones i’ll keep on medium or high include these, if i go into VR, many of these will be turned off.
Off Screen Terrain Pre-caching>
Terrain Vector Data >
Buildings >
Trees >
Grass/Bushes >
Texture Resolution >
Texture Supersampling >
Texture Synthesis >
Water Waves >
Shadow Maps >
Terrain Shadows >
Contact Shadows >
Windshield Effects >
Ambient Occlusion >
Cubemap Reflections >
Raymarched Reflections >
Light Shafts >
Bloom >
Depth of Field >
Motion Blur >
Lens Correction >
Lens Flare >
Glass Cockpit Refresh Rate>
As far as i can tell, the heavy-hitters are.
Clouds
Texture resolution
Texture synthesis
Texture supersampling
Buildings
Trees
Grass/bushes
Off-screen terrain pre-caching
Terrain LOD
Render scaling
Ambient occlusion
I stand to be corrected on any of these points though 