I haven’t seen RPM at launch make much( if any difference) in 60 foot or ET, footbraking or using a brake.
Talking a 9 sec 3350 pound car.
Just have to experiment with rpm to where the car consistently hooks and works the best. I would probably start out somewhere around 3600-3800 and see how it likes it. And adjust from there.
Mine liked around 4100 best.
On the same night, racing two classes, one on a 400 pro tree with brake, other class footbraking, car would ET the same off the foot leaving at 2000 as off the brake at 4100, 60 foots were typically pretty much identical as well.
Moving the RPM around most definitely will effect reaction time though, lower the launch rpm, the “ slower” your reaction time will be, higher, “ quicker” reaction time.
Just what I have seen
I am not a proponent of the common belief a car is faster off the brake, because I have never seen it myself. I think it also has a lot to do with the convertor well sorted to the combo too.