Note that if you want to have the Native AMP experience then you currently need to add the amp theme support flag in your theme (or via a plugin), as can be seen in the demo site's theme repo. Without this flag enabled then the legacy post templates will be used as opposed to the templates from your theme. (See wiki docs for more info.)

The Native AMP capabilities in v0.7 is really a first iteration on the feature and it is primarily aimed at theme developers who are writing new themes. In future releases it will be much easier to enable AMP on existing themes in v1.0. This release will also include theme support for all of the core themes.