You don’t need 4K textures to look good! That’s where the disconnect is, I think.
For comparison, this avatar of mine has been optimized such that no textures on it are above 1k:
Same for this one – (excepting the logos on the shoulder, that’s a single 2K image):
Now, these are PCVR avatars, so things are quite different. Shader features let you cheat a little bit. On Quest, you’d have to do all of this with smart UV mapping. I’m illustrating that having massive textures does not equal high quality.
However, I really don’t think it is advisable to tell someone to use 4K textures, and then turn around and disable mips to save a little bit of filesize. That’s the wrong order of operations.
Dropping to 2K will chop that texture’s size by 75%, and if your UVs are good, will not affect appearance. If things appear blurry that you want to preserve detail on, it means your UVs are not mapped well, and you should consider re-baking in a new layout.
You should also make sure you’re viewing the avatar from a reasonable distance. A meter away is ideal. If you’re shoving your editor camera up in a texture seam and see a difference when you drop from 4k to 2k, well… that’s expected. Instead, you should be checking from where 99% of people will be seeing the avatar – a meter away, at eye height.
FWIW, I’ve seen some Quest avatars with basically no detail across their texture – the one I’m thinking about is a flight suit that’s basically just black across the entire texture. I was confused by its VRAM usage, so I looked at it, only to find that it was using 8K textures (!!!) for that giant swathe of same-color space. Sixty five million pixels, all black!
Dropping mips to fit into a filesize really shouldn’t ever be a course of action you take.