This mod adds more dynamic shadows and realistic lighting in almost all interiors in the game! I personally didn't like that there weren't enough dynamic shadows! Now almost every light will cast dynamic shadows and realistic lighting in every interior and exterior in the game!
This is not compatible with Shadow Stripping Fix mod which is already in STEP, but I believe it fixes many more instances where shadow stripping occurs. There is a list of all the interiors and dungeons in the readme with around 100 places already completed. The author has also stated that 20+ dungeons and fixes will be added to the mod every five days, so there are many fixes still on the way.
After testing this for around an hour, this mod does exactly what it says it's going to do and seemed to be completely compatible with RLWC, but I'd recommend to load this before both esp files from RLWC. I'm not using RCRN, so maybe someone else can test the compatibility.
There is no performance hit on more powerful rigs, but the nexus site mentions a small hit to low end rigs. I loaded this on my laptop and could see any drop in performance.
Overall, the extra dynamic shadows from the interior lights is a nice touch to Skyrim.