This is an obnoxiously complex topic especially when it comes to memory management and loading/unloading stuff you don't need.
In terms of performance, embedding them all in a spine skeleton (or two, or three) is the best way to go as well as the only way to use Mesh shape/deform to tweak your size and scale for your various characters.
That being said, my 3rd character example w/ functional Unity example is called Equipman. It will literally be the golden ideal of how to deal with a character inventory that scales to being able to have oh say 50 unique costumes that you mix/match but also deal with loading/unloading. Probably won't be ready for another week or two though.
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