i can tell you they all work..[have not not done head lettuce]
burples work, burples plus white work, white works..panels work, bars work, led tubes work
55w, 70w,20 w, 125 w, 250 w,..higher wattage beneed to be raised higher
we are tending towards the very cheap bought from china white led tubes for economy...
you can get really close for higher ppf and the wide beam covers a fair bit of area
microgreens takehardly any light compared to kale,lettuce, basil[a touchy plant], spinach
.....higher end are the white rigid led strips.