So the idea was binned (by the original LE author), because Bethesda have already put in place occlusion culling planes where they could in outdoors areas.
Attempts were made to use them outdoors a bit but it was found they can have a bad negative impact outdoors if you are in a position to be behind one occlusion plane, which in turn is lined up with being behind another occlusion plane in the distance = You go down to something like a quarter of the FPS you had without them. Skyrim Project Optimisation SE is all about Occlusion Culling Planes, and mostly affects internal areas to gain FPS. I think there was one mod which overcame some big interior issues by splitting up the whole building into two big meshes instead of one (I think it was CandleHearth Hall in Windhelm) allowing for them to add a shadow caster or two beyond the normal limitation. The only lighting mod I use is Relighting Skyrim SE, a lot of nice changes to make things look better than vanilla light placement.
