stick to what u love and what ur good at. no point in doing something that u dont enjoy or is ur weak point.
u can act general maths if ur good. ive seen their work.. its almost like year 10 stuff, jus more expanded on - if that makes any sense.
if u want to try both 2/3unit and physics - u can. but if u realise dont like them, u can drop down to general maths and senior science (at my skool u can). or jus drop one of them. u have a minimum of 10units for year 12, and it looks like u have about 13 so u can only drop 1 subject.