I started a new long-term neighborhood and am currently trying to generate NPCs for every occasion relevant to my gameplay and adjust their appearance if needed, so that there's no unpleasant surprises when I actually play as my families.
I did some minor edits of the safe ones with Gussy Up mod, but I'm wondering if I can do anything about the appearance of NPCs such as Break Dancer, Social Worker, etc? I read that it was unsafe to use Gussy Up/Change appearance on them, but I wanted to clarify that, and if it's a bad idea (visibly it doesn't actually add the sim to the household, but I don't know how the mod actually works), is there something else I can do to change their appearance?

Specifically, I changed Break Dancer's skintone in simPE, but I need to refresh the way he looks in game. And in general, it would be useful to know if it's possible to do anything about such NPCs, for example, if they wear a custom hairstyle that I want to delete from Downloads, or anything like that.

TL;DR: Is it possible to safely edit "dangerous" NPCs' appearance?

I asked about this a while ago, and the consensus seemed to be that using Theo's Alt Sim Surgery plugin for SimPE would be safe. That way, you're able to export the unsafe NPC to Bodyshop, edit their appearance in Bodyshop, and then completely replace their appearance without creating a new character file and without having to touch the NPC in-game. The change is always instant with NPCs for me with this method - they'll look correct once I load the game without needing to use a mirror or anything else.

I can only offer my anecdotal experience, but I have been doing this for several years without problems - and I am still playing the same neighborhood I had when I started using this method.

You can refresh any sim's appearance in game using Fix../Flashing Blue on the lot debugger.

Thank you both very much, this is very useful!

P. S. Results:
The "Fix/Flashing blue" action didn't refresh the skintone, but it still works as a way to fix hairstyles, makeup, etc.
Alt Sim Surgery worked perfectly though, and it's very easy to use.