Old Union were DC, those had significant drag , 1 wire + hot lead,
ground thru the frame for the circuit return.

the newer like AXA-Basta, and B&M are Alternators, AC. those are lower drag.

The wire brush like B&M roller is an attempt to not have the drive drum hydroplane,
so easily.

hub Dynamos cure the wet weather problems inherent to bottle dynamos ..

I doubt you can run a modern LED headlight with an old DC generator.

halogen bulb maybe.. load must =3W, 2.4w head .6w rear, or 1_ 3w bulb, if not.

Regular screw base filament bulbs in 2.4w are getting hard to find .