BCAA - do they make a difference?
Do they give more muscle definition even if I stay with my current weight lifting regime?
*thats what I'm looking to get from using them ;-)
Will it even help with muscle definition from sprinting exercises or just weight lifting?
When have you found the best time to take them and do you go off body weight for the amount you take?
Does it help with burn off unneeded insulation?
Probably not much.
There may be some use for them if you train fasted, but they're not anything special. This is assuming that you get your daily protein requirements without them.