Low Wifi performance on Netgear R6220 and Netgear WNDR3700 after upgrade to 23.05.0

This loosely reminds me something I read in another thread ...
Quick and dirty solution would be to erase the wifi config and rebuild it.

All your tests were performed online? So they involved also routing and internet traffic.
Perform tests from LAN to wifi, I'm using huge file transfers for example. No routing, no internet.