1.Framework: Bootstrap (customize it as per your need, exclude unnecessary things)

2.font-family:Arial,Helvetica,Roboto,sans-serif;

3.I am not a big fan of amp, you can achieve similar via hosting your static pages on S3 link with cdn for faster delivery, but caching can be big problem for deployment, so you need to have versioning with in url

4.light/dark theme: specify a class on first child of body theme-dark or theme-light and then write css accordingly

5.please specify your lowest configuration device to understand what minimum you want to support for your client