Hi Neel,
If you have a headless account (db authentication) creating/owning the data, managing domains, etc. you will not have to worry about future user changes to the environment (e.g. user turnover, new users, etc.). A headless user can be easily managed by a single user, or multiple, and you can change the password as you wish if necessary. If the geodatabase system tables are owned by sde, then that sde user mapped to the geodatabase is your geodatabase administrator, no need for a new user called "sde_admin".
OS authenticated users are certainly helpful for efficiently tracking edits, versioning, etc. in the geodatabase. So if you would like to use OS authenticated users, then it sounds like a possible configuration could be having a db authenticated user create the data and domains, then map OS authenticated users to the database and grant necessary privileges on the datasets that they will be editing.
Extra documentation:
Privileges for geodatabases in SQL Server—Help | Documentation
Modifying and deleting attribute domains—ArcGIS Help | Documentation
Hope this helps!
Colin