Forgive me for not knowing who you are, but we need a bit more information to really help you answer this.
If you’re talking about any of the current generation cars (981/982/991.x) then everything I’ve read about this suggests that the PSM is extremely good and that if it’s stepped in to do something, then you’ve already screwed up and should be thankful for the help.
It does not slow you down.
I think you might be getting PTV (torque vectoring) mixed into the discussion with regard to rear brake wear. If you’re using PSM so much that it’s causing extra brake heat, then you might just be a bit of a maniac.
Finally… just my personal stance on this… I’ve NEVER turned off the nannies on the track. The only time I ever had them off was during IDS when the instructor turned them off on the skid pad.
It seems to me that if you’re good enough to not need them, then they won’t do anything anyway.
It’s possible none of this applies to some older cars. I have no idea how intrusive or not their systems might be.