Yea, I like keeping my veg plants small and compact, then flower them, usually. If they go long veg periods, try and keep them compact so they explode out of the gate, and don't have the big stretchy. That's the big factor here.
3 weeks IMO, is a really good starting point, and those plants 79 has up there in his first picture, is a pretty good place to start IMO, for most any indoor grow. Bigger is certainly not always better for the indoor grower.