Are PWA's or websites that are turned into apps on new Edge suspended in background like UWP apps are? Are they draining your system more or less so than UWP apps? And are they sand-boxed like the other type of apps as well?
Yeah, well you could use resource monitor in Windows 10 or performance analyzer in Windows 10 ADK to measure them properly. for example Spotify has a web player which you could add it as a PWA and it also has a PWA that is in Windows store. the one in Edge insider obviously uses the Chromium engine but the one installed from the Windows store uses the EdgeHTML engine from Edge classic, since it is the official WebView system inside Windows 10 for now.
my guess is that the one using EdgeHTML engine will use less system resources :)