I would highly recommend Cluster Manager. You have support, so you have a license to use it already included in your subscription.
The purpose of Cluster Manager is to make it easier to deploy and manage clusters. It sets up LDAP multi-master replication, multiple redis cache servers, file system replication, stunnel (to make sure there is a secure enrcyrpted channel between oxAuth and Redis), centralized logging, and several other pieces necessary for HA.
Using Cluster Manager, it's also much easier for Gluu to support your clustered deployment, because you will have a standardized deployment.
Perhaps you can schedule an hour call with Zico to go over cluster manager. Once you understand it, I think we can help you start planning your migration.