No doubt you’ve seen this question a thousand times. My buds aren’t pretty. They seem airy. The weed shops sell tight nugs, my stuff looks like shake. If I were to cut off all the extra leaves, there’d be nothing left.
You want 35 to 40 watt per sq foot. No x amount per plant. 1 plant could need 600w if scrogged. Autoflowers are known for a looser bud then a photoperiod fyi.
A typical canopy for the average hobby grower is 2 to 3 feet by 2 to 3 feet per plant, therefore the 200w rule of thumb. It all works out in the end. Both methods are equally valid when used for realistic plant sizes.