@Stromgarde: There shouldn't have been a significant drop in performance using the QTP3 pack vs the vanilla pack. Especially not a 10+ FPS drop just because you're near the IC. I would strongly suspect there's something more going on there, especially if the IC is heavily modded.
Thanks, Arthmoor. Since installing RAEVWD it seems to have mostly resolved my prior issues with yellow distant objects, as well as made the world much more immersive, so thank you.

I've been doing some more testing with OSR's FPS management turned off to get more accurate numbers and at least from what I've seen so far there does appear to be a performance difference at least on my rig, even outside the IC area. For example, I was wandering around the Great Forest (all ULs installed) and my average FPS was 35-41 using your core RAEVWD textures, while wandering the same areas with QTP3 low res textures my average was more in the 28-34 range. Certainly still playable, yet a noticeable difference nonetheless. Other than just swapping the textures and running TES4LODGen again (which I'm not sure was even required when just swapping textures, but I did it anyway just to be sure), my setup was exactly identical.
There do appear to be some rather noticeable file size differences between the QTP3 low res textures and your core textures, e.g. in some cases that I looked at some of your core textures are ~11k while the equivalent in the QTP3 pack is over 40k, so I guess I was assuming this would have some kind of cumulative impact.