Just as a friendly heads up - if you're doing 5.5, you're still in 802.11b legacy... legacy mode sucks the hell out of airtime - even though you might set the rate to 5.5, 802.11b requires management frames to be set at 1 - and then we have the legacy preamble...
Challenge here is most consumer router/AP's - you can set to 11n only, but they still do 11b legacy - and there, things can get complicated if one has ERP stations nearby - not just on the local WLAN, but also adjacent WLAN's - so the neighbor with an old HP printer can mess you up and put one into protection modes for 2.4...
as a reminder - OFDM starts at 6 - and that is a much better place with ERP (11g), HT(11n), HE(11ax) modes in 2.4...
Even on old chipsets - disabling WPA and DSSS support - it's a 20 percent improvement in throughput - I've been doing a fair amount of work on ath9k/ath10k along with mt76 - and the improvement is real...
QCA WiFi 6 drivers - not quite at a point where I can do useful things - closed source works fine with QSDK...
Yep, I know, unfortunately if I set it to 6 or 12 my Panasonic TV and Blu Ray (both draft N) won't connect. Since they're the only things that connect to 2.4 (and sometimes my phone if it doesn't switch to the outdoor AP when I go outside), not a big deal.
My beacons are at 5.5 though, B is disabled and no B devices can connect, confirmed that much in the CLI and by cracking out an old laptop with Lucent PCMCIA card just out of curiosity. As far as I know the beacon rate is what management frames use also, maybe I'm wrong on that.
My outdoor AP is set to 6 since nothing draft N needs to hit that. I actually bumped it to 12 for a while to completely disable CCK rates including 11 but it got a bit too short range.
My 5Ghz is set to 6 minimum and 6 beacon, mostly because that's what the asus supports via the GUI and saw no reason to script it to force 12. All legacy rates are disabled on that band which is good enough for me.
The impact of "Auto" "N Only" "N/AC Only" and "Legacy" in the asus GUI are very un-intuitive. Setting it to auto with "disable b" will disable CCK rates and sets the basic rates to 6 and 12 (with 6M beacons) until it senses a legacy device then it enables them. Setting it to "N only" sets the 5.5 minimum and beacon rate and keeps 11 as the other basic rate, but it never changes them, that is static. Setting it to legacy enables all rates starting at 1. Similar on the 5ghz band.
For my setup with those draft N devices needing CCK, "N Only" is the best choice. For those without that compatibility problem, auto with "disable B" would probably be the best choice, though a nearby G device could potentially re-enable some rates you don't want randomly.
Basically I really don't need high performance on my 2.4ghz so it isn't really a concern. I think last time I tested it it was pushing about 65-70M on a 144M link rate which is pretty much all you can ask for anyway.