Once you've setup a domain for your collection, publish mode gets activated automatically.
That means you will have to publish changes to your doc site. This prevents your customers from seeing unfinished work or drafts.
This is also a good thing because we publish the docs to a global CDN so your documentation site is a bit faster, providing better user experience, and better SEO.
Publish mode also activates clean URLs, removing any randomly generated components in the URLs that you see in the staging environment.
Oh yes, the staging environment is still hooked to the realtime changes to your collection so that you can see how your progress looks like.