I suggest that you guys look at some grow journals on youtube. Both cobs and qbs. People are growing outstanding bud with led lights. There are several lab test results also. Google spectral graphs for cobs and also hps. The led spectrum is better than hps, which is good enough to grow great bud too. Some guys are adding far red to cobs. I don't know the results yet. Hopefully, we can get some lab test results to see if it adds anything. Other that flower initiation.
After using cobs, I see the benefit to having several points of light converge over the canopy. I guess it is even more with boards. I prefer this to one light source that is spread over the canopy with a reflector. par test results for different hps lights and/or reflectors show how much the intensity drops off on the edges. It also shows why a 4x4 is good for 1000 watt hps. It can cover a 6x6, but it won't cover the entire canopy with intense light. Why grow plants that you aren't going to give intense light?
When I say 4x4, I mean the canopy. Some people will want space to move around and get a 4x4 tent and grow in the center. In that case the light is not covering 4x4, its covering that growers canopy. Then 600 watts may be good. There is a grow on youtube where a guy uses 4 1000 watt hps over a 4x6. Actually, it is two 4x6 canopies and 8 1000 watt hps lights. It seems crazy, but he yields crazy too. Its hard to have too much light, but it gets to a point where it doesn't make financial since to add more.
There are many different ways to do this right.