Good options
St2 is one of the better subjects I have studied in terms of actuarial exams, very practical, not much in terms of learning lists, more to do with preparing the student with industry expectation. I have studied st5, lots of lists, very long lists, very good if you are planning to do pensions in industry, but also interesting in terms of understanding all the transactions occurring in the investment market at the moment.
It won't make you an expert in Variable Annuity (VA) investments, though I'm not too sure what combination of subjects would be best for that - there appears to be a large variety of jobs involved in this area recently.
I have no experience of ST3.