I have had the B&M IQ-X, Toplight Line Brake Plus, and SON Edelux II on various bikes over the years. While the Edelux reflector is designed by B&M the light beam itself is much better focused on the road than the IQ-X. I find the IQ-X beam to have uneven dead zones to it. Not a bad light, but compared to the Edelux the overall build (auto function quickly failed on it, although manual on/off still functional) and beam quality leave something to be desired. The B&M taillight works nicely with either head unit. My two cents worth, anyway.

I ordered my lights from Europe (Bike24, Bike-discount, and XXcycle if memory serves), which was less expensive than US sources, even when factoring in the higher shipping cost.

In my experience, aiming such bright (focused or otherwise) lights is key. I try to keep the light beam level when setting up. Seems best way to keep focused beam from blinding oncoming traffic while also lighting the way. My simple method is to use the level function on my phone pressed against the light face to tweak it every so often. I managed to blind oncoming traffic when a spill caused the light to go out of level, so I try to check it once a week or so.