Can different handguard mounting methods affect accuracy?
I think it's well enough established that a free float handguard can improve on the precision of an AR because it reduces the number of factors that can affect the barrel, thus reducing variability in "barrel harmonics." In other words, it reduces the amount of contact the barrel has on other objects which can change the way the barrel vibrates and moves. These minor changes affect the path of the bullet and reduce the precision of the rifle.
Is it possible that different handguards and different methods of mounting them affect precision as well? If such minor effects on the barrel change precision significantly (statistical significance, not practical), it seems probable that differing methods of mounting a handguard as well as the physical properties of the handguard itself can affect precision. Has any testing been done on this matter?