Is there an API that returns consolidated metadata including layouts?

I think you might be referring to the brand-spanking-new UI API.

https://developer.salesforce.com/docs/atlas.en-us.uiapi.meta/uiapi/ui_api_get_started.htm

User Interface API enables you to create native mobile apps and custom web apps with your own branding and look and feel. A single REST request returns enough metadata, layout information, and data to display, edit, or create a record.