What Training should i do?

There's nothing to scared of when pruning, you're in veg and don't have to worry about them flowering by themselves so you can always keep them in veg until they get over an stress or anything before you go to flower. I wouldn't say you're at the point of needing to prune yet anyways. I usually lollipop (remove leaves and small growth on the lower 1/3 of the plant) 1 week or so before I flip. I see you've already done a little training, there's several different ways you can continue to train. You could put up a scrog net and tuck the tops under the net as they grow to keep the canopy level. You could continue with plant staples, clips, etc and keep training the tops to stay even. You can top any branch, not just the main, every branch you top will become 2 branches.