It does depend on the student. I also aced a math degree.I did not do 1 or 2. I took good notes in all lectures that I attended and these were my primary reference when it came to revision time. I used very few other resources than the notes I took and problem sheets given out in class. I did have friends who used books and took no notes.
Same for me. #3 all the way. In second or third year PDEs (cannot remember which), I simply sat down with the book and did all the problems. Went to class only to write and collect midterms (much to the displeasure of a regular attendee friend), at least one of which I aced.
I took good notes in my undergrad math and physics classes, but never computer science. My degree was in computer science (minors with math and physics), and now I'm a computer science researcher.
The reason for the discrepancy was that the lectures were quite different. Math and physics lectures tended to be focused on problems, and how to do them. The professor would walk through example problems, explaining as they went. I diligently wrote all of that down, and would refer to it when I did my homework. I found writing down the examples as we went a good way to make sure I was actually understanding each step.
I never took notes in computer science classes because the lectures were more conceptual - beyond the first semester, the professor was never walking us through how to code. They were explaining new concepts, not showing us techniques I would have to reproduce. I didn't see much reason in taking notes about concepts, I would rather think about those concepts during the lecture. I found taking notes a distraction. The only exception here was some algorithms lectures, where the professor walked us through how to prove particular things.
Basically, if I was being shown techniques, I wrote down the techniques. If I was being told new concepts, I just listened.
However, all of us who did well did 3.