neowin[.]net/news/mozilla-firefox-is-now-available-in-the-microsoft-store-for-windows-11/
microsoft[.]com/en-us/p/mozilla-firefox/9nzvdkpmr9rd?activetab=pivot:overviewtab
Now that Microsoft's allowing Any app into their store -- UWP not required -- figured Firefox would be an ideal test subject to see how this works. In my Win10 Insider VM, running 21H2, first updated the store apps, which got me the same store that's in Win11 -- eventually everyone running WIn10 will get the new store. The store itself still borders on useless -- searching for Firefox found books but not the browser -- but it's a new GUI to I guess confuse us a bit more.
Using the 2nd link above, installed quickly, putting the app in the special folder with all the other apps from the store, "WindowsApps". Still got new folders in ProgramData & in the User AppData folders, same as a normal install, and in Settings -> Apps, Firefox gives you the options to move the installation as well as uninstall. Unlike the original store apps using UWP, uninstalling Firefox Did Not remove everything. You can't see inside the WindowsApps folder, but the other Firefox folders remained, and only around 600 of the 20k+ registry entries it added were removed [in contrast a normal install adds about 600 new entries].
I can't say that's how every win32 app will work with the store, but my guess is that most will. The only advantage to installing these apps using the store that I can think of is that if you've got multiple copies of Windows using the same account, e.g. on a laptop & a PC, if you install an app from the store in one copy, it'll be there, ready to install in the 2nd.