Pretty close IME. 30w/sq ft works for COB and QB type LEDs. For example, the HLG 550 is 480w and will flower a 4x4. A bunch of those QB type boards are 240, 280 and 480w. Lines up pretty good for 4x2, 3x3 and 4x4. 35w will work for some strains but it's good to have a dimmer to bring it down when needed.