Switching Off the 5GHz will Not improve anything.
Give each Radio its own SSID, and use the same WAP2 (AES personal) for both.
Wireless clients that can use the 5GHz Radio will show both Radios in the available Wireless Networks and you can try one or the other ans see wahts work better.
Single radio clients (2.5GHZ) will not even show the 5GHz as available.
You should know that in many environments multiple APs are needed to provide good Wireless.
In many cases there is No Magic Wireless Router that can cover whatever One desires.