Orbi: We really need separate SSID for 2.4 Ghz and 5Ghz or speed is limited to less than 200 Mbps

TheEther Respectfully, you need to reread that Apple link more carefully. It does not state a different roaming threshold for 5Gz. What it says is that 5Ghz APs are usually overlapped at the -67 dBm level, and therefore macOS clients will hang onto an AP longer than expected. (Due to the -75 dBm roaming threshold, you can travel far into another APs zone before the client will switch.)

If you are reading something else that I missed, please correct me, but here is the passage:

"macOS clients monitor and maintain the current BSSID’s connection until the RSSI crosses the -75 dBm threshold. After RSSI crosses that threshold, macOS scans for roam candidate BSSIDs for the current ESSID.
Consider this threshold in view of the signal overlap between your wireless cells. macOS maintains a connection until the -75 dBm threshold, but 5 GHz cells are designed with a -67 dBm overlap. Those clients will remain connected to the current BSSID longer than you expect."