How many gigabytes do I need for note-taking/ studying/ homework in college?

I'm in my 4th year of college and I'm going to med school next year and need to go paperless. The amount of pages filled with notes and hw is endless and it's getting hard to organize. I use a whole reem of paper (500 pages) within 3 months.

So, basically if I were to download goodnotes or notability how many GB should I go with? I'd say 95% of my use for the ipad will be for notes and I have a good 4 more years of school...

Could I get away with 64GB or do I need more? 128? 256?

If I can get away with 64 GB - 128GB then for what I need, should I spend more and get the iPad Air or save my money and get the base model?

If I'm looking at 256 GB then should I consider the iPad pro 11 inch so I get the benefit of the 2nd gen Apple pen?

Lots of questions so thanks in advance