It puts two rev limiters on your car. One when the car is in motion and one when the car ISN'T in motion. Thus they can set a rev limiter (when car isn't in motion) around say 3k (because you like to launch at 3k) you can hold the gas pedal at WOT and launch from there. Makes it easier.
Maybe if you had street tires. Two steps are made for racing and most people that are serious about racing and use two steps run on slicks so no you wouldn't tear up anything.