I topped for the first time the other day and was just wondering if the "would have been" popcorn buds actually turn into the two main shoots? The new shoots are coming in but they would have been useless popcorn branches hadn't I topped.
If I understand you correctly, yes. At the point where the fan leaves' stems come out of the main stem secondary branches grow, when you top your plant the top 2 secondary branches take over so you basically split your plant in 2 but it also encourages lower down secondary branches to grow a bit more and just generally bush out. If you want to know more try googling secondary branching or something.