I guess it depends what you are looking to accomplish.
Do you need a controller for redundancy, at a local Layer 2 network? If so your best option is to enable is as a standby-master. This way it will sync all configurations. When you enable redundancy with VRRP, all devices should connect to the virtual IP address. If the Primary master goes down, the VRRP IP address will flip to the standby, and it will promote itself to master state. All APs can then fail over to the device .
If these controller need to be service clients at the same time, i think you will need to configure it as a Local controller. If the Local is in the same L2 network as your master, you should be able to still setup Centralized licensing redundancy. If they are in sepearte L3 network, I am not sure of the best approach, but i have a feeling centralized licensing wouldn't work for that.
Long story short, i believe you will want to setup the second controller as a standby, and install it in the same vlan as the master.
_ELiasz