Shell rot is dependent on the water quality of the aquarium. We don't know what exactly the conditions are to cause it, but we do know improper water conditions will both make it harder for the mantis to fight off disease, and nitrates/phosphates often help bacterial growth.
Lighting also affects this in some way. We don't know if the fungas/bacteria is photosynthetic, but we do know Mantis Shrimp get stressed out if they're exposed to high lighting for long periods of time, in which the stress can lead to said immune problems.
Theoretically, if you have the water quality really good (like SPS good), and you provide the O. Scyllarus with the proper burrowing conditions, you should be able to get away with a soft coral tank.
IIRC one of the longest living peacocks was in a reef tank fwiw, but that's not implying its best conditions are not dark.
I can't answer much on the lighting units, but LED reef breeders are doing my toadstool rather nicely for years now.