Yes, Firefox Focus is for mobile.

What features of Firefox Focus would you want to work on your Firefox for Windows?

Well......the instant cookie & site data deletion upon closure seems helpful.

You can set that on regular Firefox using a checkbox here:

Settings page > Privacy & Security panel > Cookies and Site Data section

You'll notice a Manage Exceptions... option for sites you want to stay logged into from one session to the next (since you need to keep their cookies for that).

Firefox Focus is primarily designed for mobile devices (Android and iOS), which is why you’re seeing the QR code prompt when accessing it from a PC. It doesn’t have a full desktop version, so for similar privacy-focused browsing on your computer, you might want to use standard Firefox with enhanced tracking protection or private browsing mode enabled.