Yes, why not? With a core of Bio, Chem, Physics, any of your options are good, really.
RS is essay-based, so yes, it is work (any subject is), but I think that EPQ is more work if you do it properly, because you have to do research for it (can be more or less depending on topic) and write a long essay. (And if you don't do it properly, it's not really worth doing it IMO.) On the other hand, unlike RS you could do EPQ over the summer, so it would distract less / be less work during term time than RS, and it would mean you have fewer exams than if you take RS.
Bear in mind you'll also need time to do work experience / volunteering if you are serious about medicine.