1. Would it be wise to get the textbooks for my subjects now and start taking notes during this break?
No, enjoy your break (plus textbooks may change).
2. When should I start taking notes, now or mid January since uni starts early march?
Once University has commenced.
3. Should I have two books for each subject, that is, one for textbook summary/notes and one for notes taken during lectures/class?
I use to just print the lecture slides and scribble on them for my in-class notes for the majority of my subjects, and then do practice questions/tests in the form of notes. Some subjects it may be benefit to supplement using textbooks, so keep seperate notes from your tutorial/lecture slides.
4. Do unis heavily rely on textbooks for study/revision or more on in class notes?
Similar to school, it depends.
For example, one of my law subjects it was like 3-4 different textbooks, tutorial notes, then lectures with respect to depth.
5. How ahead should I be in my content before starting uni?
Do not start, you deserve a break.