Pre-Workout in a fasted scenario (30 minutes to 2 hours prior to workout) to help with mTOR activation and also for muscle-sparing effects.
Post Workout and with a high content (followed by a Post Workout Meal) to help with protein synthesis and optimize the benefits of the Insulin spike, given that carbs are in order.
Yes they do help increasing recovery speed, many studies on it have proven muscle soreness decreased on the supplemented groups as opposed to the control groups. I personally like 4:1:1 and 8:1:1 ratios. Though for an 8:1:1 ratio it's pretty much better to go with Leucine by itself anyway, look into SNS Bulk Leucine if you want the best Bang for Buck on Leucine, if not the 8:1:1 alternative would be USPowders Bulk ...and for fasting purposes and good recovery also check AI Sports Nutrition .