With Mutable plugin you’re able to generate customized skeletal meshes. Generated Skeletal Meshes are identical to the usual ones. So, yes, it’s essentially baking all customization into a SKM. You are fully in control how many skeletal mesh components it generates, how many mesh sections (material slots) each have, and UV and texture manipulation to assist with combining sections together. There is no runtime cost once SKM is baked, (there is a slight overhead because additional component in the actor, but can be mitigated as well)
Here is the documentation that covers pretty much everything: