so I've read about foot on brake and then pulling back both paddles to get a confirmation for launch in sports plus or race mode. But when I do , I get nothing on the dash. Does TCS need to be off? Or do I just forgo the paddles and just plant the throttle to the floor and launch? Most other cars have a confirmation light telling me launch is active. Does it not work similarly on the gtr?

On the GTR, the paddles have a different role.
When in race or other modes ( idk if it works in C) mash left foot on brake and right on gas. If your steering is perfectly straight and car is in operating temps, the race start activates. At this point the paddles will allow you to adjust the launch rpm.