This is how to know which server is a PUb or Sub...

Go to CCM admin page.....system....cisco...cisco Callmanager.....search for the server either by using the server name or leave a blank field in the find space and click find.

This will return all the servers in your cluster..

click on each server and look at the top right for a parameter called CTI ID:

your Pub always has a CTI ID of 1.

And to your second question, Yes! always make changes on the Publisher...it is a must! Never make changes on your Sub.

Hope this helps....