You can use any computer you want. It is usually enough with something like a raspberry pi (A raspberry pi can be pretty expensive, so you should look for an alternative). Then just connect some external drives (or internal based on the computer).
You can download an acsm file for the book after borrowing it by loading https://archive.org/services/loans/loan/?action=media_url&format=pdf&redirect=1&identifier=BOOK_ID
I recommend knock or DeDRM Tools for downloading and decrypting from the acsm file.
I have made a script for automating some of the process.
I have made my own program for handling metadata link. It makes it easy to tag files and search for them afterwards. It’s still not finished, but it should be working. It’s currently only a cli program.