The old FourSevens Quarks used to rotate the tailcap the switch between modes. I’ve got one of the older QT2L-Xs that’s probably my favorite light ever for that reason. That and it’s the perfect size for pocket carry while still being decently bright. The newer models since they got bought out ditched it which sucks because it was such a simple interface.
I got a couple of Fenix lights recently that I don’t hate. They still do the “cycle through modes with a button” thing, but it’s at least a dedicated button separate from the tailcap switch.
Wattage = V x A.
They’re pointing out that it’s impossible to hold both wattage and voltage constant while changing the amperage.