does the document root file remains the same as primary domain or there is another home/domain2/public_html
Yes the public_html stays the same for the main domain on the hosting, if you add a second domain, you will see a new folder created with the same domain name in your root folder.
A second domain would have a directory of it's own.
You could either place it at /domain.com or /public_html/domain.com ,
They do not have their own public_html folder.
It's recommended to use a /domain.com folder
Trying to help everyone I can :)