Choose a major which you will enjoy and choose a school where you will be in the top 25%.
If you very sure about medicine, apply to few BS/MD programs and few UG programs. Also you can choose a school which will yield the best GPA. It does not have to be Ivy or Top 10-20 schools. But if you are not sure then it may benefit to choose strong UG school for your career plan B. Here choose a school or major which allows to change major.
As a HS Senior you are anxious and looking a firm clear answer. But unfortunately there is nothing called best. Beauty is in the beholder’s eye. Same way, writing 15-20 pages essay some one will enjoy and will breeze thru where as the same person will hate to do a working programming project or solve a complex math equation and vice versa.
Various folks can give guidance based on their own family experience or based on the collective knowledge by following and responding to various posts over a period of time. No one can say choose this major or this school because no one knows who you are and what triggers your drive, passion, natural ability, intelligence etc.