FIRST GROW, PLEASE HELP, LED VEG CAB, BLUE DREAM BABIES

The dreamers are coming along beautifully, but as we near week 3 im really starting to think about training and nuts. Any advice on topping vs lst? I think im going to top Form, which probably means another 2.5 weeks of vegging.
Will the root mass grow alot during flower? Should I transplant to bigger pots with that much more veg time? My seedlings are coming up hard and they're about to get some much larger pots, probly not taller, but definitely girthier.
Im smokin so the questions are kinda pourin out, if anyones in SF, hit the Sanctuary for that earwax!!! ANY ADVICE IS MUCH APPRECIATED! HAVE AN AMAZING DAY!