I don't know enough about instant center (IC) and anti squat (AS) to know exactly why it does what it does; but I do know that removing the bind from the upper control arms and fixing the pinion angle are definite bonuses.
I've got my right foot planted to the floor after the apex of the corner.The MM Torque-arm plants the rear tires much better during acceleration than the stock four-link design, and the Panhard bar locates the axle much more precisely. Your Mustang's overall performance will be greatly improved, with much better acceleration out of corners, along with improved handling, stability, better straight-line launching ability, and increased predictability.