If childhood taight me anything, the minimum is just 2 buttons. Forward, reverse-left. Simple, usually effective, and maddenly oversimplified. I think I liked the one that only sent forward more, but it of course required a track.
People forget simple things like steering servos were not available to most kids until the 90s injection molding explosion that is so ubiq today.
Totally forgot about one of the cars I had that did that. Though, I always hated it thinking it was such a cheap toy.
There was also a model that had "forward" and "spin counterclockwise".
Weren't there single-button ones that would continuously drive forward unless you pressed the remote control button, which would switch it to reverse-left?