Bulgarians can be incredibly humbling...the real problem is most people do them incorrectly...
^^^WRONG
^^^WRONG
^^^MUCH BETTER
I would personally never elevate the front...the people who typically do, do it mainly because they think they feel a better "stretch"...but all you're really doing is shifting unnecessary stress to your knee, hips, groin, and lower back...
holding onto to something to aid in balance is fine...I usually hold onto a side of the power rack...back foot elevated ideally by just your toes...the ideal descent should not focus on your knee touching the ground, but your hip crease reaching parallel with your knee crease while your torso remains as vertical as possible...glutes and quads are utilized the most, and driving through the heal rather than through the front of your foot should be the main focus during the ascent...
some focus on tempo, static holds at the bottom and/or the top, or simply controlling each rep...there's really no wrong way...most people are pretty surprised at the carryover something like a 50lb dumbbell with these for reps can transfer over....plus there's no mistaking the burn in your quads and glutes when done correctly...4 x 8-10 is pretty common, while the 12-15 rep range with any real respectable weight will have most searching for a pacifier.