When searching online for plugins/info/etc on pass, search for 'zx2c4 pass' to eliminate lots of noise. passff for FireFox and a couple of options for Chrome too. That way I can always access my git remote offline. While I could store it on github or drop box or some other cloud location, I keep my git remote on a USB stick. Qtpass uses git for password syncing to other devices/cloud. This also allows you to share a password store, as you may share say, a bank account, with your spouse and you both need to get into it. qtpass can encrypt passwords to multiple keys, which is recommended, as one of your keys may become lost, stolen, or defective. I generate the private key directly on the yubikey, so the private key has never been on any other device. Qtpass uses the PGP key storage slots on the yubikey. qtpass is also single factor, but using the yubikey instead of a password that could be guessed. That's essentially single factor auth using password on the store. The other password managers, afaik, have a master password and only use u2f for online login to your account. The cheaper u2f security key won't do what I describe. This only applies if you have a full feature yubikey Neo/4/4c/etc.

Yubikey last pass