We have selected to view clients only and have tried switching between 2.4 and 5Mhz but some maps refuse to show any clients despite us knowing that they are there and connected and reported on in the clients view.
You can certainly just broadcast an SSID to 5ghz (or 6ghz) but for 2.4Ghz it will allow 5Ghz also. This is done with the checkbox on the network policy wireless networks page. as shown below.
Not sure if its the same on the Physical controllers as the cloud version but when updating AP's in the cloud hive it allows you to select a checkbox that lets you choose the firmware version you apply to individual AP's. I have not experienced any ...
Have updated the settings and it is showing one of the clients now. However under "monitoring" the floor shows more clients than are displaying on the heat map?