roof height and grow area's canopy.
if you got the space, then you can experiment - 2 plants of same genetics in one single pot, and others plants just in their individual pots. i lean towards the result that 2 plants in a single pot would produce about the same amount of yield as a single plant, given the same pot size and same vegetative phase duration.
so, you would want to pot the 2 plants in that single larger pot, than the others planted in its single pot - maybe... larger pot would mean longer time for the roots to fill it, larger pot means larger plants, at trade-off of longer vegetative growth phase so that these plants fills out the larger pot.