Settings
There is a meta box in post/page screen. You can setup some options for each posts/pages.
Enables the Twig template engine on the post/page. If you want to use template in the post/page, you have to check it.
Visual Editor sometimes breaks template.
If you want to use template in the post/page, you should check it. Then, visual editor would be disabled only to the post/page.
If you want to restrict users to write template by security reason or so, you can disable content editor for the post/page.
Post/Page screen for non-admin user:
Post/Page screen for admin user:
