Unlike Tesla, Mercedes will still come with a physical key that you can still use in addition to the iPhone. You also have a method to disable the physical key and place it in the car, and only use the phone, but you still have a key just in case, that you can always reactivate anytime (provided you get the door open, probably with roadside assistance).Seems like a risk on the part of Mercedes, counting on Apple like that. I'd assume there is a default of their own at least. So an M1/M2 can only one run external, does this count as 1 or 3 external monitors on an iPhone?
As for Apple CarPlay in its current iteration, it will only take over the center screen of the three monitors. The rest remain MBUX. They do allow Apple CarPlay to show multiple rows of icons and it does take advantage of the larger real estate however. It literally looks like a giant iPad, with multiple rows of icons rather than just the standard two.