Usually I don't bring a bag of stuff to campus with me. Nor do I bring a bag, or anything else, home at night. I work when I am on campus on my courses and service. I work at home and on campus on research, and have books I need randomly in both places. If I need a book I don't have with me, too bad. I'll use that book next time I am working the other place. The only exception is if I get a book in the mail or from the library at the last minute before leaving the office and want to take it home.
I have many bags, and tend to use them to go to a coffee shop. Then I pack for that particular outing. A computer and a few books.
I don't take notes when I read. I'll underline (only secondary sources, never defacing a primary one). When I need a quote, I take it directly from the book to the document I am writing. That way I am never transcribing from my own bad handwriting. You have to check a quote against the original book anyway. I still do that, but if I am careful the first time there won't be as many mistakes in transcription. I tend to work on things I've known about and been thinking about for years. I do include new information if something new comes up, but generally I am working out a new formulation of an old idea.
I do take notes when I am thinking. I write a blog post or write in notebooks. When I write, though, I rarely look at these notes.
Process be damned, the reader only sees the final product. In other words, the amount of effort or the difficulty of the task does not matter to the reader as much as it does to the writer. Translators are notorious for this. They think that if they wrote vertigo, changed it to dizziness, changed it to vertigo again, then back to dizziness, then back to vertigo, that that is different from just writing vertigo in the first place. Well no, from the reader's perspective there is no difference.
So carry stuff around in a bag, or not. It doesn't really matter.