Hi Ron, you have four controllers in the setup. I usually recommend to design the deployment in a such way that one geographical area (e.g one building) is covered only by one controller, or controllers in HA/FF pair. In this case you don’t need to enable mobility . Although if you have one area with APs homed to different non-paired controllers, you better enable mobility since the controller from other pair does not have a session information from the first controller , and potentially it is a roaming issues.
If you have only a pair of controller covering the same area, make sure that FastFailover checkbox is also enabled (along with HA) - thats how controllers exchanging session information.