[ovekvam]

If you want to rely on the car to regulate the traction control, you are better off with the throttle pedal floored. If you accelerate without traction control (DSC Off), you need to modulate the throttle yourself. But in this case, you will have the electronic (fake) differential brake to help you gain traction.

The amount of slip that will give you the best acceleration varies with tyre type and ground conditions. If there is snow of gravel, you will need more wheelspin. Soft winter tyres will also like more wheelspin than low profile R-compounds.

The car will have to guess how hard it can launch, and it doesn't know how grippy tyres you have and how slippery it is.