T-Mobile Home Internet is my ISP. There is a Gateway that acts as a modem/router/AP and is also the DHCP server. QoS can negatively affect throughput on this LAN so it is recommended to turn it off. However, my router is in AP mode and I don't see that. There is a WMM mode however. I tried to turn it off but when I do, the password no longer works and any given device is unable via WiFi. 

This same issue was reported on another model in a different section ot the TP-Link Community. The answer given was only that WMM should be turned on with no explanation about why the password no longer worked. It would be nice to resolve the password issue as well as know why WMM must always be on or if WMM can be a bottleneck.

Thanks!