Burning and bleaching from LED's is usually caused by the diodes being run too hard, or having too tight a lense on it. This will give you hotspots when you run the light close enough to the canopy to get a decent PPF. It's not the LED's themselves, it's the way they're being run. I've run cxb3590's 8"-10" away from my canopy at 50W (<50% max power) without bleaching or burning, and I've run The Cannon 12"-14" away from canopy at 240W(<50% max power) without bleaching or burning. This is towards the end of flower, without any reflectors or lenses.
Some companies will put a tight lens on a weak diode so they can rep. a high PPFD over a tiny area. This will give you hotspots too, bleaches and burns along with it.
Watts per plant isn't a good measurement in my opinion, because what's a plant? Is it a 6 foot tall Jumanji monster or a 1 foot tall clone to flower in a Sea of Green? Watts per square foot isn't perfect either, but assuming you're dealing with high quality COBs then 37.5 watts per square foot is a tried and true method for maxing out your space.
I'm an organic grower so I like to have 4-6 big ass trees per 4' x 4' with 600 watts of COBs overhead. If you have enough power in your lighting you can get a full canopy with a good 2'-3' depth and get major yields. People get great results with 9-12 smaller plants in that space though...
My company's light is 240W, (
my AFN Forum), and I'd say two big plants or three medium plants is perfect:smoking: