for the popular uni's (UNSW, Western, Newcastle) there are no subject prerequisites, for Usyd med, a 2u maths background is sufficient (and at least a B4 in it), and idk about other uni's. so the subjects you've picked so far are perfectly fine, as long as you can get a competitive atar with them, for med this would be 99+ or even 99.5+. as sonic said, this means you'll need to perform well in your lower-scaling subjects like bio and PDHPE which isn't impossible since you're good at them, but you'd need to aim for B6 in all your subjects not just these two in order to get 99+. so yea your subjects are fine, in fact any combination of subjects is okay if you're going for med, you just need a competitive atar (and/or ucat and/or interview, but it's way too early to be worrying about these)