@bandit306, there is no 1 size fits all, the ideal pot is highly dependant on how much space you are giving to each plant. From personal experience 1 gallon pot is enough for a plant to fill either 1 or 2 sq ft of grow space.
This is a plant in a 1 gallon fabric pot in a space of 2,27 sq ft.
Same plant just before harvest
In a more recent run I had that same 1 gallon pot filling half that space.
Either way it does not constitute SOG, which is using more than 1 plant per sq ft. I’ve done 2 plants per sq ft like this:
4 auto plants before flower stage
Same plants just before harvest (2 colas per plant)
Now, fabric pots are great, but they do rise humidity quite a bit and I’ve noticed no difference yield wise. Currently I’m trying 12 plants in square plastic pots in that same space in (I hope) true SOG single cola style.