I picked up my carbon pack M2 a couple of months ago and have done a couple of autocross with it so far in stock form. I'm very impressed with the performance of this car out of the box on the stock star spec Pirelli tires, I actually was able to FTD my second event, vid below.
The car's weight is a non-issue for me and it feels rather nimble for the overall size. I do feel the springs will need to be stiffer with some grippier 200tw tires and have purchased the M Performance HAS kit to see how that will pair, but in stock form, the car drives beautifully.
As for setup, I found 31F/33R psi tire pressure cold worked best for me and the M Mode setup I use is as follows
Engine: Sport - Sport+ is fun for the street but is way too touchy for on-the-limit driving and Sport gives a more linear throttle.
Transmission: S3
Chasis: Sport Plus - As autocross is mainly on a smooth surface I tend to go for the stiffest setting to allow for better weight transfer and stability through slaloms.
Steering: Comfort - This one surprised me but I feel there is way more being translated through the steering wheel in comfort vs the overly weighted steering in sport. It also helps give the car a lighter feel while being more precise and delicate.
Brakes: Comfort - I found sport brakes to emulate a lot of initial bite without much modulation while comfort had a lot of the braking range at the bottom of the pedal but was easier to modulate.
DSC: Off
M Traction Control: 0 - This is a personal preference as I don't like being tripped up by the TCS cutting power/applying brakes all of a sudden while I am mid-correction. I did play around with the M TCS and all the way up to 5 doesn't really do that much at lower speeds, it just progressively gives you less throttle the more slip angle there is but it still lets me get very sideways, and didn't help improve my time. Maybe next time I will try 6-10.