As a 26" arrow shooter, a longer arrow out of the same draw weight may be about 30-36 grains heavier (if shaft weight/inch are identical), but I don't think the draw length matters as long as the draw weight at the different draw lengths is identical. Once the arrow leaves the back of the bow, no more force can be applied to the projectile.
Of course if one is using a bow that is 40#@28", the 26" draw will produce less energy out the front than any longer draw would.
I have only shot one big game animal that I consider not thinned skin ( TX boar). I've shot bear, whitetails, mule deer, and pronghorn with 2 and 4 blades. Great placement, sharp, and stable arrow flight = dead.
By the way, that Boar wasn't even shot with a "broadhead". I was a guinea pig (no pun intended) using a -4 cable bladed "head" called the atom. I was astonished at the effectiveness of this head. However, I never hunted with it again. Boy, I'd bet it would should hammer squirrels though!
All said and done though, I'm more comfortable with 2-blades even though I have no poor reports otherwise.
I should add, it has been 47 years since my last physics class, so I am more than grateful to be reminded.