In that space you could put a 400w if your ventilation was real good. U want to change the air every 2 minutes in a perfect world.
We put 1 plant under a 400w, veg it to 1ft and then turn it. if its a stretchy sativa then we do a tie-down before turning.
I have found fewer plants do better than more due to competition for light.
Wether you put 1 or 100 plants, there is the same amount of light and air.
More plants can be quicker for sure, but in oz laws are based on plant numbers. if yr caught with 1 plant u get a slap on the wrist.
pretty good if u can get 3lb off 1 plant under a 1000w.