There is also extra bones (the wings) on the smaller character that the taller character doesn’t have.
Well, you’re buying models that aren’t made to go together. I would assume just renaming the bones & matching the rest pose would work as long as the general structure (i.e. hierarchy) is the same (e.g. spine_1 → spine_2 → spine_3 → clavicle_l → upperarm_l → etc.) Plus, extra bones (like ponytails or extra arms) are alright.