Ubiquiti is hardly a common CPE, pro/enterprise grade WiFi equipment client management is a whole other story they balance based on anything from spectrum congestion to usage congestion on individual APs and the handover protocol between APs doesn’t use deauth unless it’s a very crude implementation.
There is roaming support in management frames and for signal strengths clients usually do their own roaming if you have 2 APs on different channels for the same SSID your client would select the best on and roam if necessary as the signal strength changes.