Athosanswered grow question 6 years ago I would transplant before flowering, to a 20 liter pot, to give the plant more space for the stretch. As for separating the colas, sure LST works great, tying down the branches helps a lot in keeping the canopy even and is not stressful at all.
As for defoliation, be careful if you've never done it and only do it after the stretch is done, at day 21 of flower if you want to.