802.11r is a roaming protocol standard to complete fast transitions when clients are moving between different APs.

Enhanced roaming feature is to make sure no clients are sticky and remain connected to one AP even though they have weak RSSI values or SNR threshold.

If you have both enabled, then the enhanced roaming feature will make sure clients are not sticky, and 802.11r will make sure that 802.11r supported clients will roam seamlessly to other nearby Cambium APs.

The 2 are totally independent because if the clients are at a state where it refuses to roam to another AP, then enhanced roaming will disconnect the client so that it can look to move to another AP with stronger signal strength. So in this case once a client is disconnected, roaming does not come in to the picture, since it will be a new association to another AP. And for those 802.11r supported clients that are not sticky and follow the right standards of triggering their own roaming thresholds and try to roam to another AP well within the SNR threshold set for enhanced roaming, then they will follow the 802.11r Fast-Transition protocols to roam to another AP.

Keep in Mind, Not all client devices support all of the protocols designed for seamless roaming. 802.11/k, 802.11v, and 802.11r