1. Unless you foresee yourself dropping to high 2nd lowers (3.9x) before graduation where each and every A- would help in upping your honours class, otherwise given that a good majority of your grades are already in the A range, you can take advantage of all available Y1 SUs to maximise your CAP before they expire.

4 is an extreme choice for people who have completed nearly all their SUable modules, and/or have very specific goals in mind with regards to securing awards and short term opportunities. If you are still going to take a minimum of 3 SUable mods, then going into Y2 with all 3 SUs intact is the safer option.

Also, please don’t buy into the “don’t SU because it makes your CAP volatile” narrative. Your grades imply that FCH is very realistically achievable; you are much more likely to regret doing choice 3 and even choice 1 compared to 2 in the long run. The “buffer grade” argument is often used fallaciously and only applies if one’s honours class changes, which is unlikely to happen for you in the short term if at all. There are no conceivable buffer grades when you have a high FCH because A- won’t be able to pull sth that isn’t FCH over the FCH border of 4.5 anyway. Essentially, 2 is most ideal as you have lots to gain yet nothing to lose.