If you take a look at the pros and cons of decoupled/headless CMS, “no visual preview” is at the top of every list of 'cons'.

When we set out to build next-drupal, solving this issue of content preview was a top priority. This is why the very first version of next-drupal shipped with inline preview for editors: edit, view, review and publish your content right from within the Drupal admin. Seamlessly.

We are now adding personalized preview mode for decoupled Drupal.

What’s personalized preview mode?

Drupal ships with an advanced access control mechanism with support for roles and permissions. In Drupal, you can set field-level access for your content e.g. giving access to an editor to view an image field but not to regular users.