You can create your own custom feeds, respecting the specifications of the Content API. Once these JSON content feeds are created on your website, you'll be able to add them as sources of your sections, using the Custom connector.
The values handled by the app are simple. Each element inherits from the Item type, and has some type specific attributes (like articles, videos, events, photos, ...).
More info here https://www.goodbarber.com/help/custom-feeds-r111/how-to-create-custom-feeds-a287/