do the vroid characters have skels?
Why not use the one from the vroid fbx
or
you will have to possibly delete a couple of “leaf bones” that blender added to the tips of things
like your wobbly fingers
or
load ther vroid model with its own skel then in unreal retarget the the other skel to the vroid skel then you can disable certain bones in the retargeting manage to fix it
I can’t give you details, its trial and error to make sure the bones match
but I do think you have leaf bones adding in blender on your fbx export