If I make a policy change on my primary node is this replicated immediately ? is there a logfile showing the replication ?
It is replicated as soon as you hit Save Changes. The actual data of what has been hanged on a node is part of the audit.log, which will show you that a remote user has change the settings.
For the actual cluster communication, MWG doesn't provide a special logfile.
I can see the audit.log on the primary node but there's no audit.log on the secondary node, replication seems to Ok but it would be comforting to see a log showing the changes have been replicated.