Now, this isn't a big deal for me as I don't care that much either way whether snow rim shading is on, but I was pretty curious as to what might be causing this!
I can enable all features of the improved snow shader in BethINI (sparkles, etc.) EXCEPT the rim shader. When I check that box, I get an immediate CTD on attempting to load a test save. When I uncheck rim shading, I can load that save without issues. Weird, right?
The only mods I can think of that touch the snow shaders that I have running are Cathedral Landscapes and Obsidian Weathers. Not sure which one is winning in regards to the snow INI settings right now but I doubt it matters. I also have ReShade and ENB.
If anyone can suggest any other type of mod I should be suspicious of in regards to this crash, that would help narrow it down. It would be nice to save someone else a bit of confusion or trouble with this issue in the future. If I simply missed reading some fine print on a mod somewhere, feel free to roast me.