I agree with the sibling; I think Apple's attention to UX is going to inform them that physical controls are good on a car, even if physical controls on the front of a phone (a la earlier iPhone models) are unnecessary.

I do assume it'll be a locked-down, walled-garden experience, only serviceable at Apple Stores (which will open garages at some locations), assuming they can get away with that legally. They'll reject any non-Apple-genuine part, of course.

But to your point about voice control, I do expect Apple will try to make that really good. Touchscreens suck for keeping your attention on the road when you want to change the heat temperature or change songs or stations. Physical controls are better. But good, painless, non-frustrating voice control is by far the best option for avoiding distractions and keeping your eyes on the road.