Both activate in the same way (ESP off-Dynamic/Sport on, Left foot on brake, right foot flat to floor, left foot off) Launch control will obviously control the launch with electronic intervention, a brake torque launch will have no electronic intervention, you'll be at the mercy of traction and driver input only.
In fairness, other than ability to hold revs for longer, there's very little real life difference between the S-Tronic/DSG and the ZF Tip box for launching. In an S-Tronic/DSG car, a launch that breaks traction will be rudely intervened by a short shift upto the next gear, in the Tiptronic, this is not the case, you'll just slide about in 1st until you hit the change point to 2nd.
I launched my TTRS over 250 times at the drag strip so I'm very well acquainted to Launch Control capabilities and limitations. With the RS6, I must be on around 25 launches off the brake so far. Those worried about a few launches and possibility of damaging the torque converter, nope, chill, I'm the test guinea pig