what's the target face count for the new topology ? then decide how that target is divided up on head, body, wings, claws etc (it should probably be in the same ratio as the high). Then it's, as above, a testing process to see what works best to achieve the goal... it'll probably be a combo of trad normal mapped geometry…
With such overhangs, looks like quite some work when re-topologising. A possibility I would explore, would be just slightly protruding scales so easier to re-topo but possible to stick in separate, instanced "hero" scales. Probably would do some tests before, to evaluate the option (does it save time?, possible to hit…