Page URL Routing
URL patterns on a headless site are usually configured in the frontend framework (such as Next.js or Gatsby). Wagtail by default, resolves URLs to pages using their slugs and location in the page tree.
The impact of this is that "view live" links in the admin may resolve to the wrong URL, if the URL patterns configured in the frontend framework don't match the page structure. If rich text is rendered server-side, this will affect any internal links in rich text fields too.
Resources
After you've set up your Rust and worked yourself through "The Book", you might want to check any of these resources
News
Wagtail API - how to customize the detail URL
Customize the Wagtail API endpoints to suit your needs.
Deploying Wagtail to Heroku
Heroku is a great platform which takes away much of the hassle of system administration when trying to deploy a website, but it has its idiosyncrasies which you need to know about when trying to deploy Wagtail.