You'll study whatever ever you think is appropriate next term.
Then you'll get your first assessment back and decide you need to study some more.
You'll think you're prepared for the second assessment, only to find they've ramped up the difficulty. So you'll decide to study some more.
And so on.
If your aim is to get the maximum mark possible in X2, there is no such thing as too much study.
If your priority lies with maximising your ATAR, then you need to put a limit on your goals in X2 (unless you are an absolute genius).
It is up to YOU to strike that balance based on your relative abilities in each subject. With luck you will get it right just in time for your HSC exam.