Is there a reason why you don’t just want to make the “author archive” a page and list them all on the page with a shortcode ? If that’s an option, simply put your single author template in author.php
Author templates – Template hierarchy
If not, you could take your current template (that you’ve put in author.php) and move it to archive.php with a conditional tag, only showing your authors if the query is for post type authors .
Conditional tags – A post type
But any way you do it, I don’t think you will get the permalink structure you’re asking for:
domain.com/users/user_name/ABOUT
But rather :
All users (using the archive page to list all authors): domain.com/archive.php
Single user (or about-page): domain.com/author.php
If you instead were to use a simple page and a shortcode you could get:
All authors: domain.com/users
Single user: domain.com/author.php