All right, while I wait for my partner in crime to wake up from her nap I'll tell what I know.
I started out at the age of 5 shooting. I started with the simple pinch draw and when my bows got heavier I graduated to the two fingers on the string pinch grip. We used the simple one bowfishing where we often only pulled to our chests.
Drawing an arrow to me is a set of calculations as to how much of the bow's energy to put behind this arrow to get it to go where I want. I did not always pull to full draw-I learned my bow's energy intimately and used it to determine if I needed a full draw or a chest draw. With a heavier bow that chest draw snap shot can still be lethal. I practiced both draws extensively-sometimes a whole day shooting at cornstalks during summer break. The goal was to lodge your arrow in the cornstalk from 10-20 yards away. Bisecting it worked too.
In college I studied Asian archery. A full draw there is longer than either draw I knew. But using pinch grip put me in good steading for using thumb draw then.
My arrows growing up were barely notched with a knife to sit on the string. They also had more bulbous nocks to assist with the pinch. Pop had a set of two-fletch with built up sinew nocks. Pity they're gone now. But they're made nothing like today's self nocks. A Turkish nock is closer to what we made.
As to the lethality of Native bows and the records of them shooting? Pop's warbow had to draw 90#. He could hit a dime at ten yards. He could stalk silently enough to count coup on an alligator. He had mastered the so-called "Parthian" shot if something presented itself on the fly. I have often wondered if he truly was magical. I never outshot the man. I could draw more at my max, but he was always the better shot. I've seen better shots, like the two gentlemen who can hit a thrown aspirin, but I've never seen a better overall hunter.
Pinch grip with the right equipment is just as lethal as any other style, and lends itself to shooting rapidly and flexibly. The lack of a predefined anchor point leaves you more able to determine your arrow's trajectory, which can mean the difference between dinner or no dinner. I know it's not "proper form," but we developed it to an art form here before you guys ever arrived to tell us we had it wrong. Even having been taught Manchu archery, I still prefer what I learned. I just know it better.
If the sun's still up when Karen wakes up, I'll get a picture of both types of draw for you guys. I'm realizing this information is about to die out-I need to preserve it any way possible. People who learned like me are few and far between now.