it would probably be a spring controller on a target for splineIK which is probably what Spring Magic does for you automatically (though I've not used it) :/
As @Neox said, if you're using normal maps, you really should not need to do anything special like transferring custom normals or other convoluted workflows. Make sure: * Your triangulation matches between modeling app, baker, and target engine * Your tangent space matches between all apps (generally this is Mikktspace…