@Szusi 

As for the wireless speed issue you reported, please help confirm below:
1. What kind of devices are connected to the wireless network? How about the link speed on it? If it is a computer, you may check it like below:
https://www.tp-link.com/support/faq/2265/
Note: If the link speed is not as good as expected, please try with another computer with a more powerful wireless adapter. BTW, tell us the model number of that wireless adapter that runs on your computer.
2. Please ensure the QoS is disabled on the AX20 or try to reset it to the factory defaults, then reconfigure it from scratch. You can check this:
https://community.tp-link.com/en/home/forum/topic/257504
3. Try to disable the Smart Connect on the AX20, then modify the 2.4G and 5G wireless settings on it, such as wireless channel and channel width. It is suggested to run a Wi-Fi analyzer to find a clear channel, then change the channel width to 40MHz for the 2.4G, and 80MHz to 5G, reboot the router and reconnect to the wireless network, then confirm.