Ive been using PWAsForFirefox for couple of years now and it's pretty good tho a bit clunky at times as firefox updates tend to break some settings.
And reading through this article seems like I'll be sticking with PWAsForFirefox:
web apps in Firefox will not use a minimal browser frame and will continue to show a main toolbar with address bar, extensions, bookmarks – though the ‘new tab’ button will be replaced with a button to open a normal Firefox window.
Lame.