While granted out of a perfectly tuned bow all (or most) broadheads will fly better and group much closer, it would seem it would be impossible to group all 100 gr. broadheads in the same spot out of a well tuned bow.
In my opinion, the difference in drag between broadheads, at 20 yards would be not be easily measured. Pay close attention to Len's Trilogy. I'd put a lot more emphasis on tuning the arrow if you want to see results like what we're talking about. However, all three are important. The only reason a properly aligned broadhead will plane more than another, is because the setup is not tuned correctly to shoot it.