Highlighting rentals?

Dumb question, but I’m an incoming 1L and trying to decide how I want to go about my textbooks - physical or digital. So many posts suggest renting physical & highlighting/annotating in margins. Are you allowed to mark up a rental book though?? In undergrad I feel like I remember the bookstore checking to make sure the book was in good shape before you returned a rental. Dumb Q but trying decide what I wanna do so just asking

Also - any backpack recs?