Quick alert about a good post:
Coaching Torso Positon on Split-Squats
I love Bulgarian Split Squats. I use them with everyone, basically, for strength, balance, and hip health.
Want to emphasize strength? Bent over torso position.
Want to emphasize loosening up those tight hips from sitting? Upright torso position.
Also note that he sets up from the bottom. I use this a lot.