I heard that LED bulbs only, no good as they lose the beam pattern and spray light all over the place, it's the bulb and glass together that determines the beam pattern, I could be wrong just my 3p worth.
I upgraded my headlights with Phillips GT 200 xenon bulbs, same current draw, 2x luminance and straight swap in non sealed units, twice as bright in my garage, but never driven in dark
they will have a shorter life span compared to halogen, but hay ho.
You would need three relays wired in to work the high and low been together, this is to stop the voltage drop through the wires and giving poor illumination this is because your dividing the voltage by four and not two. Also you need the relays in so you don't overload the light switches and burn them out.
I've got two extra relays in mine at present to stop the voltage drop and switch overload, I have the third relay in a box, but the wiring is in my head at present, hope that makes sense.