None of the routers will go higher than the FCC max, which is something like 120mW (20dBm) if i >remember correctly.
It seems to be very true at least in this particular case (unless I am seriously mistaken).
I began to monitor the power consumption of the device while changing transmit power in GL Web interface and OpenWrt Advanced section (I tried to reboot the router after each change). First of all those transmit power levels shown the GL Web interface and OpenWrt Advanced section don’t always match (can be 0 dBm (10mW) in the OpwnWrt options and “High” in the the GL Web, secondly the power consumption of the device with both radios on ( OpenVpn (AES128) , idles around 460-550 mA.
2.4GHz is WAN (OpenVpn cleint is on), a wired client is connected to LAN, another wireless client is connected to 5GHz. When the wireless or wired client runs speedtest the current consumption jumps to 700-740 mA.
Changing transmit power for 5Ghz client from 10 to 1000 mW (reboot, restart) does not change the total current consumption of the device meaning that most likely the output transmission power is locked to a certain value. I wonder why is that since for example in Canada you legally can go as high as 1000 mW for certain Wifi channels. I have seen on Amazon Alpha USB powered wireless adapters also mentioning 1, 2W output levels - are those numbers are also totally meaningless in real world applications? On the other hand, realistically speaking, how it is to possible to power a radio transmitting 2 Watts with 5V / 0.5A?