Your problem is relatively familiar. It seems we have an inconsisteny in what is given to NPCs equip, and what can be equipped. Sometimes this comes from the new item given to them is missing their target model completely. It’s different from a simple missing texture.

The mod that’s creating this issue is also the one that touches each of your errored (nude) NPCs. Since it’s on major vanilla characters, we know where we can start looking, specifically at the items placed in the problematic NPCs’ inventory, like the other user said.

Based on what you said, that you’ve installed a mod list, I think the most likely problem is that your new clothes and weapons plugin(s) are being over-written by something different later in your load order.

If you do the old binary two-step and disable half your new mods, or armor mods, and try to replicate the issue, that usually helps. You’ll notice that everyone will be back to normal once you have deactivated the culpable plugin from your mod manager. After this we simply and patiently enable half of the newly disabled plugins until we see naked NPCs again (yay). Finally you’ve singled out the broken plugin, you can either reconfigure it’s load order arguments or FOMOD or just eliminate it completely.

Good luck and godspeed