well all i can say is that the asus you mentioned is more than capable, so if the config wasn't the issue then i don't know why it didn't give you what it should have.
WiFi 6 support in routers is already there, however if your client doesn't support it then it's a waste of money for now. i have the asus RT-AX88U with wifi 6 support. i upgraded the wifi card in my laptop to a killer ax1650x, which gives me a wifi connected speed ot 2.4Gbps, however the drop off is quick, and to get the 2.4Gbps i am so close to the router i might as well be connected via ethernet.
wifi 6, though, isn't all about the higher speeds, it's more about be able to support many devices without degradation.
i finally went for the Ubiquiti UniFi Dream Machine All-in-One Router. Weird thing was , it took over 90 minutes of trial and error and numerous HUB 4 resets to detect the VM internet connection. Seems to be rock solid now at 925 Mbps down and 52 Mbps up. I think now a better managed home network is more important than wifi 6. Ubiquiti managed switch with PoE and AP for upstairs is the next step....
aww man, what a mistake buying that piece of junk. i had that for a few months and then sold it on ebay.
what a piece of junk it was. have you noticed the insane fan noise it gives when it does anything over 25Mbps? even local LAN file transfers causes the fan to ramp up to insane levels.
i was a big fan of ubiquit fit before buying the UDM (having edge routers and unifi APs), however that has turned me sour to them and i now won't touch them with a barge pole. their support is one of the worst i've come across, and you end up havint to run beta versions of the Unifi OS to fix basic features they broke in the release versions, but the beta versions break other things in the process.