Hello OGB-NIKO,
The following is from our Wing Clustering document:
Active / Active or Active / Standby
The configuration of your cluster will require a mode to be established for the desired operation within your environment.
In a large enterprise / NOC deployments with several thousand or more Access Points, the cluster mode must be set to Active / Standby in order to maintain statistics and other information in the UI / CLI. Active / Active should only be used in small / medium size campus deployments with MINT tunneling where Access Point load balancing will actually provide a benefit. Other deployments will not benefit from Active / Active setup whatsoever.
The general recommendation is to keep clustering in Active / Standby for most of deployments for fault tolerance, ease of troubleshooting. Note that Active / Active clustering is not supported for the NOC controllers managing remote sites.
I have uploaded the latest Wing Clustering Guide, which has everything you require for Wing clustering (Active/Active or Active/Standby).