Yes to to all questions.
Truthfully, creating a PWA with NetTalk is trivial. A PWA in of itself is not complicated. Getting certain features to work on all devices not so much. For example, iOS can be a real pain in the arse due to Apple's unwillingness to implement the standards everyone else is following (Chrome, Firefox, etc.). Safari on iOS is lagging way behind.
NetTalk has the tools to do just about anything you want in the world of PWA's, disconnected apps, and so forth. Just takes a little extra work.
Don
Here's my latest and best Google Chrome audit on my PWA and some screenshots of the app: