Upon selecting Reader Mode as the AMP experience to be enabled, the AMP plugin offers a list with all known AMP-first themes, as per the AMP Plugin’s site Ecosystem page. This will:

• Enable support for non-singular templates , such as the blog index page, category template, author template, and other such archive templates.
• Enable brand synergy between the AMP and non-AMP versions of the site (Site logo/icon, Color palettes, etc.)
• Enable key functional components, either as part of the theme or via block plugins: 
• Enable the AMP plugin developer tools are available in Reader mode