Is it better to just do Automotive engineering or do a combination of mechanical and electrical engineering?
Specifically I would do Mechanics and Power and I want to do research and development for an automotive company specifically doing propulsion systems. Things like drivetrain and the engine. Since the future is electric power, I think it is a good idea to have the knowledge of electrical engineering as well as mechanical engineering,
In general, I do tell students to find their passion and go after it. It sounds like you have found your. The other side is to be flexible and finds ways that your passion can be applied in more than one area.
Automotive Engineering is a degree that pigeon holes you for a specific industry. My only concern with that is that the economy goes through ups and downs and in a down market in automotive, it may be a little more difficult to find a job outside of that industry.
Majoring in Mechanical and Electrical Engineering or Mechtronic Engineering in much more flexible. This can be applied in automotive, aerospace, consumer electronics, medical devices, etc.
The truth is that an automotive engineering degree can be applied broadly, but having the people reviewing your resume to understand that may be more difficult.
You have 2 great options. Neither choice is right or wrong.