Time will show! WebApps are normally located at web servers because of their special needed environment and will get access via a Web-Browser like Edge, Chrome, and others. On a local machine to run a Web-App, via a Web Browser, there would be the need of a local Server like XAMPP, AMPPS or other. If those PWA's will run on Edge Browser on a local machine, I believe that the needed Server parts are on MS Server and will get access by just 'installing' a kind Runtime on the local machine. That will hold the used space on the local Machine very low, but what will be seen on that local machine, is just a fraction of the whole needed software. What will be installed on the local, will not be able to run on its own without access to the Internet over a Web Browser.
Regarding Web-Apps, I don't like to use them on 3.party (Cloud-) Servers, I want or even need 100% control over that apps. A simple fact is, any Cloud running apps, also send all data via that Cloud-Server and those data could all be captured, in other words, nothing is secure! There many Program Languages which could be used for to create such apps, HTML, PHP, Phyton and many others. Databases are MySQL, MS SQL, MongoDB and many others could be used. Web-Apps mainly are small programs, as long as you the user didn't use MS Acces or the like to develop such apps.