1. Prototyping, I'm not sure. No-code app builders, the clear winner right when it comes to PWAs is Bubble.io.

Although, the folks at Softr are doing very interesting integration stuff with Progressier as we speak.

Now, these two platforms don't have an export function. The best option for that is Webflow. You can use their no-code builder to design your app, and then export the code and host it yourself. Which will also work great for creating a PWA. I can't speak for the quality of the code, but from what I've read, the exported HTML/CSS is decent quality, but the JS is hard to work with afterwards.

2. I haven't, but it shouldn't be a problem integrating with them. From a technical perspective, to integrate Progressier, you really just have to do two things: add a script to your HTML template, and upload a file to the root of your domain. So pretty much any framework or build tools should allow you to do that.