Have you asked around your classmates and see what they use in their efficient workflow?
On youtube, search for paperless student, she reviews apps and shares her perspectives.
Personally, I use Notability to do my notes and annotate pdf documents/slides. It does not have an endless canvas like OneNote, but this makes export to pdf easier. Notability searches handwriting too (provided that is not too sloppy)… it’s search function is much better vs OneNote.
I am a visual person and like SimpleMind on iPad quite a bit.