just upgraded all my APs (3x Archer C7 v2) to the latest version of OpenWrt.
At first I upgraded one unit by using the sysupgrade firmware and with that I started to experience a decrease in the 5 GHz range of about 20 %!!! No settings changed.
So I thought it might be the "dirty upgrade" and upgraded all my APs by flashing the whole firmware via TFTP and after first boot did another settings reset.
Then quickly setup them up again as dumb APs, without using the old config files. I configured everything from scratch.
Still the WiFi range is very bad compared to OpenWrt 18.04....
WiFi Region always set to US.
I did first try the included ct drivers which came by default and 5ghz was capped at 40 mbps while 2.4 ghz range was bad and capped to 10 mbps download and higher upload rate. Installing non ct drivers made speeds reproducibly match my expectation and surplus ap+mesh worked fine simultaneously on the same radio.
So I did another test today and for me wifi range/strength is now exactly the same when comparing latest ct against latest non-ct drivers.
The dBm values measured at my stationary clients stay almost identical, ± 1-2 dBm tolerance during the tests.