for simplicity's sake just ignore actual moderation process and go by the rank 3 int gets the 3rd highest ext score for their int score etc. etc. which is an accurate enough way of describing the real thing.
i like different things, so my recommendations wouldn't be helpful.
tho, i wouldnt take cafs. seems like the units would be better used for testing one other possible subject that you might decide to keep in y12. for me, i would do physics.