Thanks for sharing that other thread I went to read what's going on...
15 yards is about 45 feet. This seems a bit far. Curious if you can test an ethernet connection and see what speeds you can achieve? I suspect some sort of interference (my initial thought)....
I used to use NetSpot but now use WiFi Analyzer (paid version). I still have NetSpot but don't use it much. I had to access developer mode and change one setting to improve performance on my Android phone, (for both apps supposedly). Probably a good idea to see what is really going on and actual signal strength in dBm.
I'm not sure why those recommendations were made. I do not game have you tried the Game Boost feature?....
Here's default settings on my AXE16000 for 5 GHz. I don't quite agree with what was recommended to you...
If you go to the Network map section and show the list of clients, you will see the Link Speeds indicated. Do those speeds agree with what you are seeing for those devices?
I don't know what type of Wi-Fi those your two devices have as far as 2x2 or AX capability. Some gaming systems seem to use 1x1 so those speeds would be lower.
I will assume you have run tests with the second device either powered down or moved to another area of the house. I will also assume you only have one floor to deal with.
On the tx rate the ps5 is 1201 and 1080 rx rate. Series x is 866 and 390. The ps5 has Wi-Fi 6 (ax) and the series x only has Wi-Fi 5 (ac).
Not sure about the 1x1 or 2x2.
Yes all tests are done with the other device completely turned off and not in standby more. They do not show up as connected to the router. And yes only one floor.