In my experience, I've never not gotten root bound in any size normal pot. Up to 15s now and if I poke my finger in the dirt I can't go past like an inch without getting stuck in roots. I've been experimenting with various root pruning pots to try and alleviate this issue, most notably smart pots. On the same note I have heard of people growing quite large plants out of pots that seem too small by my standards, so could just be my strains or something.
I don't know exactly know what u mean by "full potential" but I would try to use a pot just big enough so it isn't root bound when u decide to flip to flower.