Perhaps I can speak to this. My older child graduated with a physics degree, was offered a slot in a top physics grad program, but choose to do her med school pre-reqs and go to med school instead.
She says that physics was the most interesting thing she every studied bar none. Waaaayyyy more interesting than medicine. But most of the jobs available to physicists are awful.
BTW, the odds of you getting a position as research scientist are very long. [I know--DH was a PhD physicist and research scientist at a major National Lab until his death not long ago. I know where his classmates from his Top 5 grad program ended up. Out of his peer group, only ~3 out of 50+ ended up in academia or in a basic or applied research job. D1 has also dated a number of physics PhD post-docs. They have generally found the job market for physics PhDs to be weak.] Most physics PhDs end up either in industry--where they will be doing applications and engineering--not research--or teaching at small liberal arts colleges where doing research is not a priority. Or they end up as analysts in variety of financial services/computer consulting businesses. Or as managers in technical industries [think defense firms].
She says the medicine as a field of study isn't all that intellectually exciting. Tons of memorization and not much basic, ground breaking new knowledge. However, she loves clinical work and dealing with patients. So awful material, great job.
Shadowing a doctor will critical in helping to make up your mind. Most people have this idealized vision of what doctor does, but the day-today reality of their job is much different. D says that with a few exceptions doctors really don't save lives--they mostly spend their time managing chronic illnesses.
Additionally medical schools will expect that you have done extensive physician shadowing as preparation for applying to medical school. You will need to be able to speak convincingly about why you want to be doctor in your application. And saying you want to help people just isn't enough.
And remember, while it sounds romantic and grand to practice medicine in high needs overseas areas--those regions may not WANT you. Also medical licensing is complicated and most countries require physicians to retrain (complete a new medical residency) when they move from one country to another. Also, as a practical matter, med school is expensive and average loan debt of new med school grad is around $200,000-$260,000. You're not going to be able to pay off your loans by doing volunteer service.