Papi has a different approach on how to work with fields and page types in WordPress. The idea is coming from how Page Type Builder in EPiServer works and has been loved by the developers.
So we thought, why not use the same approach in WordPress? Papi is running in production today and has been easy to work with when it came to adding new fields and creating different types of pages.
Papi don't have a admin ui where you create your fields, it's done by code and that's how it should be.
Only the field value is saved in the database, no reference of what kind of field or something like that. You can start with a new database and already have all fields setup.
When creating a new page or any kind of post type you get a new step where you can select those page types which are bound to that post type.
All fields existing in Papi feel like they belong in WordPress and it's easy to create your own field.