Hello! It checks for compatibility of both themes and plugins. When in the Onboarding Wizard, it scans your templates as if you had selected Standard mode wherein your active theme is used for AMP pages. If your theme has significant incompatibilities identified, then you may need to select an AMP-compatible theme for Reader mode if you can’t resolve them. Alternatively, if the active theme degrades gracefully when its AMP-incompatible markup is removed, then you may consider Transitional mode: this will make a separate AMP version available of your pages using your active in addition to the original non-AMP version.
In the last step of the Onboarding Wizard, you have an opportunity to browse around various templates on your site to ensure the AMP pages are being generated as expected.
Thanks Weston! That’s great.