never put more then one plant per container. They would just fight for root space and food, possiably get there roots all tangeled up. In fact they should be in 5 gal buckets minimum. go with the 400 watter. I would not just ask experts to answer it kinda turns ppl of from helping. We can all be experts in time if we read and learn. O 3x2 isnt gonna hold more then 2-3 mature plants. What method are you looking into to maximize harvest for that space. There lots of articules on Lst ,and other ways of getting the most from your grow.