Sure there is. A “search” is any invasion of a reasonable expectation of privacy. That includes ordering the opening of a car door, assuming that reveals areas of the car not otherwise visible through windows (as it would on my car, and many models).
Wrong. Mimms only means ordering them out of the car is legal under the Fourth Amendment of the US Constitution. It doesn’t make it legal under state law, and it would be illegal in Vermont, Massachusetts, and probably other jurisdictions that don’t follow Mimms as to their state constitutional protections.
Moreover, your premise, that opening the door is included in ordering the driver out, may not necessarily follow for all the reasons I gave in the post to which you responded.