I recently reinstalled Windows and after reinstalling all my apps, I discovered that I had both 1Password extensions installed in Firefox. I found the page on the website that says you can install one or the other, but (aside from needing the Windows app, which I have) it didn't make clear the pros and cons of one vs the other (or both). I did notice that with both extensions installed, I am, in some ways, having a better experience than before the Windows reinstall, e.g. the Firefox extension(s) now work with with Windows facial recognition unlock.
1Password Version: 7.3.684
Extension Version: 1PX = 1.15.3, 1P = 188.8.131.52
OS Version: Win 10 Pro v 1903
Sync Type: 1Password.com