Wp Subscribe Author plugin is help subscriber to follow his/her favorite author.
Plugin will automatically find the author link and display the pop card. Author link should contain the rel="author" attribute. If it's not working please add the 'data-authorID=""' to author link.
Yes, plugin supports guest user subscription option from verion 1.6 .
Yes, we can customize the template. You can create your custom code template on your active theme with the name content-favourite-author-posts.php. If you don't create this file, plugin will find the content.php from your active wordpress theme.