DFS replication role and AD replication

If I first setup the domain with domain functional level 2008 or higher, the default AD replication will be DFSR.

The DFS replication role is irrelevant here (only apply to file server replication using DFS namespace?)

I can force replication by using repadmin or AD Sites & Services without concern the AD replication is DFSR or FSR right?

and dfsrdiag is not going to affect on AD replication but File Server DFS replication only?

In test environment, I added DFS replication role, then did nothing.  But then when I try to remove the role, the error message shows "Before removing DFS Replication, remove this server from all replication groups"

May I know what to do to proceed to remove this role? 

Thanks