Well, 1 second after I start the car I immediately put it in P500 mode. I NEVER drive it in P400. What is the point of driving a car with 507 PS in 400 PS mode. I never understood that.
My tranny setting is always S5 manual shifts. I programmed my M button in the I drive at MDM on and S5 and EDC in sport. When it is dry I use the M buttom a lot especially because I like the MDM on setting. It allows the tail to brake out a bit but there is always the safety net. But, be careful: you can loose the car with MDM on (I had it on a private track. There is a limit).
DSC off is something I never do on public roads. Only when I take my car to a private airport I do. Plenty of space there and with DCS off you need that. It will bite you in the a$$ before you know it.
Have fun with it