I hope @Msoengineer won't mind if I link two of his settings screenshots but since OpenWRT and DD-WRT may or may not be using the same wifi drivers, I wondered if there were some rule of thumb settings along with some nice explanations ?
Perhaps add another with 21.02.0? There is now a "Coverage Cell Density" setting, that I believe just sets the minimum basic wifi rate. Idea being, like disallowing the legacy rate, raising the minimum rate shortens the time taken for beaconing and multicasting, leaving more airtime available.
On 2.4 and 5ghz, Coverage Cell Density to Normal (or High?)
I'm not sure why the 5ghz disallow legacy rates checkbox disappeared in 21.02.0. Earlier versions had it in both radios. The new coverage density/min rate setting is available in both.
"Legacy rates" (DSSS 1,2, 5.5 and 11 Mb) never existed on 5 GHz so I don't think setting that option on a 5 GHz radio actually did anything.
If you only have one AP for a residential household / family coverage there isn't much use in restricting range. In a public situation like a coffee shop certainly it's a good idea. I do set all my 2.4 GHz APs up to beacon at 54 Mb (cell_density 3) but running a whole house on one AP like that you may have a lot of coverage drops at the farther rooms.
I've never used OpenWRT so I cannot make a comment, but all of the principles for wifi are uniform regardless of the firmware...it's just a matter of being able to change the settings or not. Science is Science in terms of the suggestions I have made. YMMV on openwrt firmware vs dd-wrt in the settings and what they yield. I know that dd-wrt seems to dig deeper into overriding the settings, or having the ability to anyway, than openwrt does thanks to Brainslayer. He does some things with the driver that OpenWRT likely won't.
In term of coverage, it's ALL hardware specific. If you aren't running on a QCA 998x radio (Wifi-5 wave 2, or better) than you're always going to be limited by the older chipset hardware and their hard baked TX pwr limits. no firmware can overcome the hard baked stuff...
Welcome to the OpenWrt forums @Msoengineer. Not to derail this thread, but now I'm curious -- and I say this in a good way -- what brings you here? If you've never used OpenWrt, seems a tad unusual for you to spend time commenting here. But seriously, it's great to have new contributors, especially those who are knowledable, so I hope you'll stick around (and maybe become an OpenWrt user yourself).
Heh, I wondered if that was the case. Ah well, always good to eliminate a button that does nothing.
(my self educational side is now wondering if there's a good place/way to get Luci commands displayed in their equivalent CLI commands)
I was under the impression that the setting, raising the minimum data rate, mostly improved available airtime, especially with multicast. I guess raising the data rate will reduce the receiver sensitivity, and thereby range, which could be good or bad, depending on whether your in house stations are just hanging on, vs you are in a crowded area and now with less range, you don't waste as much airtime hearing your neighbors and waiting for their packets to clear the air.
I guess it becomes, as so much in wifi, another "YMMV" case, try it out yourself in your conditions and see how much it helps or hurts.
I wish there was an easy "airtime saturation" indicator, as well as a general number of packets and data dashboard/indicator. Would help with quick optimization, at least for geeky folks like us who might even want to look at that.