I'm not entirely convinced that the OP's plant is root bound, but you could certainly be right. I also have nothing against transplanting any time it is needed, you just have to prepare and be careful.
absolutely
Not true.
It works fine. But, it's more challenging to get water to the undersized plant without overwatering. (Get nutrients to the plant in timely way without getting salt buildup because you're not watering the entire container for runoff. Or, you're waiting a very long time for the container to dry enough for another full-runoff watering.).
How much longer do you have? From the pictures a week ago, transplanting now seems pointless. They look N def to me. I would supplement with some AK Fish. But, I don't think it's a big problem later in flower.
