Can someone explain to me how to use pass?
Can I use it fully offline?
How do I back it up to USB drive?
What does the day-to-day operation of Pass compared to Keepass look like?
I am trying to learn it as I want to use it, as I think that keepass is bloated for my use case, and I would appreciate any help here.
Yes, you can use it fully offline.
To back it up I believe you'd just need to backup your .pass and .gnupg directories.
I haven't used keepass, but the entry from the archwiki should give you a good idea of usage, and it also lists some helper apps: https://wiki.archlinux.org/title/Pass
Super simple.
pass list existing passphrase pairs
pass insert $SERVICE add new passphrase pair, substituting $SERVICE for whatever resource you're saving a passphrase for
pass $SERVICE print stored passphrase for $SERVICE to stdout
You will need to configure gnupg key pair before using pass, if you haven't already.