I’m aware of this plugin and honestly, I think it’s weird that a separate plugin is required for this at all.
Why isn’t this feature in core by the time 5.0 comes out. Why not let admins define whether a post type should be edited in Gutenberg or normal?
Don’t get me wrong, it works nice and looks really good for making long and fancy blog posts.
But not all post types are content/text based pages. Most of the time only posts and pages (WP core types) are.
In most other cases meta/custom fields are used extensively in combination with custom templates that handle the page templates.
I don’t see Gutenberg working nice with anything else than blog-like posts, or in other words, long pages. For simple text input it’s way too bulky (takes up all the room on the page where you would like all other options and fields instantly visible) and for page builder use-cases it’s too basic since you can only edit the part within the actual content of the template, not the whole page.
So in short, other than for blogging (long posts) and basic websites, in my opinion it doesn’t help or contribute to the way users and developers use and create more complex CMS. It will probably only sit in the way..