I've done some research on this. The Texture Compressor, as-is, can't be used. Not only does the catch-all compression in the tool (BC1/BC3 by default) result in bugs (black or weird looking textures), there's probably no point in compressing them as the different textures and maps already use BC1,3,4 or 5 compression - you can't get much better than that. Texture size however, is another story. Many textures are over 2048px (aka 2K) which is probably too much for my humble 970 GTX. So resizing these super-large textures and saving with the original compression could help. The tool doesn't do this, but I am considering working on a batch script to semi-automate the process of shrinking down 2K and larger textures to see if it helps. Although I honestly don't think this will solve the issue. I don't think it's a texture compression/size problem but rather an engine problem. Remember that Fallout 76 has a HUGE render distance compared to Fallout 4 - even with the sliders all on lowest you can still see things a long way away. Or it might be an LOD issue, I'm not an expert on this so all I can do is speculate.