@XxDaRkCaLiBeRxX 

This resolution 'might' help you as well:

https://community.tp-link.com/us/home/forum/topic/190240?page=4 

- Set your SSID's to be different for 2.4 and 5 GHz

- Manually set QOS to be what your ISP gives you, if you can't turn QOS off

- Set your 5 GHz band width to the highest available (probably 80 or 160 MHz)

WMM disable actually breaks my wifi completely, so I'm surprised that fix worked for people in this forum.

@Scope, I tried everything suggested on this thread. Unfortunately, my WiFi speeds slow down to 1.04Mbps on my Mac laptop, while it is up to 300Mbps on my IPad. The speed goes up when I reset the router, but it is useless to keep resetting it. Thinking about returning and replacing the router, unless there is another solution.

@Scope 

I am having the same issues  - -slow wifi but ethernet hardwired - fast.

Hardwired to the TPLINK router I have 30MBS down 45MBS up  this is right in line with incoming internet to the router which is 29.82 down and 33.7 up.

Speeds over wifi are 5mbs down and 18.47 up - that's trom my laptop.  From my phoneI can't get more than 10mbs upload.

I have tried with QOS on and off with wmm on and off tried separating the 2.4 and the 5 with different names - nothing has helped!! 

Very frustrating -