WP is a blogging platform from the early 2000's that still uses many of the same code conventions that it started with. It does have a REST API, and you can extend it with plugins to work as a headless CMS, but it's riddled with inefficiencies and is truly a great example of why most devs would not think to reach for a CMS if they were building a SaaS app. Can you build a SaaS app with WP? Sure. Should you? Absolutely not. WP is good for its plugins and themes, but for anything more robust, it falls apart.
Strapi is a contender that is quite similar to Payload but they have a mixed focus on "GUI-based" logic and code-based logic. You design your content models with a GUI, and access control is highly limited to a typical RBAC pattern. Where in Payload, everything -starts with code-. You can version control your schema, because it's all just a config. Deploy to other environments (stage, prod, etc) with ease. Use and re-use functions across different collections. Even access control is handled beautifully with functions in Payload, and is significantly more powerful than RBAC.
I'd say our killer feature though is the simplicity, yet robustness of our admin UI. We have many features that Strapi does not have - like field conditional logic (Check a checkbox field, see more fields. Uncheck checkbox, those fields go away). Our admin UI is also completely extensible. You can create custom field types easily just by importing React components and passing them to a field config - then boom, your React component appears in the admin UI rather than the built-in component. It's intensely powerful.
There's a lot more, but these are just a few quick points. I've been using headless WP for ~6 years, and I've always liked the idea of Strapi, but never trusted it enough to hit production. That's why we built Payload.
What you describe sounds similar to Statamic. The config and even the content is yaml files, and the admin UI is also quite extensible. But I always wish it was easier to change stuff with code in Statamic, so maybe that's where Payload shines.
WP is a blogging platform from the early 2000's that still uses many of the same code conventions that it started with. It does have a REST API, and you can extend it with plugins to work as a headless CMS, but it's riddled with inefficiencies and is truly a great example of why most devs would not think to reach for a CMS if they were building a SaaS app. Can you build a SaaS app with WP? Sure. Should you? Absolutely not. WP is good for its plugins and themes, but for anything more robust, it falls apart.
Strapi is a contender that is quite similar to Payload but they have a mixed focus on "GUI-based" logic and code-based logic. You design your content models with a GUI, and access control is highly limited to a typical RBAC pattern. Where in Payload, everything -starts with code-. You can version control your schema, because it's all just a config. Deploy to other environments (stage, prod, etc) with ease. Use and re-use functions across different collections. Even access control is handled beautifully with functions in Payload, and is significantly more powerful than RBAC.
I'd say our killer feature though is the simplicity, yet robustness of our admin UI. We have many features that Strapi does not have - like field conditional logic (Check a checkbox field, see more fields. Uncheck checkbox, those fields go away). Our admin UI is also completely extensible. You can create custom field types easily just by importing React components and passing them to a field config - then boom, your React component appears in the admin UI rather than the built-in component. It's intensely powerful.
There's a lot more, but these are just a few quick points. I've been using headless WP for ~6 years, and I've always liked the idea of Strapi, but never trusted it enough to hit production. That's why we built Payload.