TL/DR: This supposedly "1800 Mbps" router can't break 250 Mpbs; the Netgear router it's meant to replace runs circles around it. What gives?

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I bought a used Deco X20 this week, hoping to replace a Netgear AC wifi router that has never performed as expected. My home has a 1GB fiber connection, and my 2021 M1 MacBook Pro is usually connected via ethernet through the router. With that setup, I generally get ~230 Mbps on wifi and 900 Mpbs on ethernet.

The 5 Ghz range around our home is mediocre, so I wanted to finally kick that router to the curb and get a mesh/wifi 6 system. After reading reviews on several options, this one seemed like a solid price/performance choice. It has not turned out that way so far.

After setting up the Main unit, which is just under my desk, I am getting — at best — ~220 Mbps on wifi and 250 Mbps on ethernet. And yes, I have isolated the latter, right now I have wifi turned off on my MBP and I can't even break 100 Mbps. 🤦🏻‍♂️

I've tested with an older MBP and my iPhone, the results are the same. This late model MBP has an 802.11ax Wi-Fi 6 card, if the Deco X20 supports up to 1800 Mbps then I should have no trouble getting close to my fiber speed of 900 Mbps, but at the very least I should be matching that speed with ethernet! 

Am I missing something here? I've gone through every setting I can find in the app and online dashboard.

Other things I have tried:

• Fully reset the router, I started with it that way last night.
• Made sure the firmware was up to date, it is.
• Ran "Network Optimization."
• Identified the ideal 5 Ghz channel, at least with the Netgear in place — 149. But of course I can't change that with the Deco, it's stuck on 40 (I had read that the admin for this was simpler than usual, but WOW it is anemic).
• Turned off UPnP, turned on IPv6 (though I don't know if my broadband uses that).

Any help is appreciated. If this doesn't turn around then I'm back to square one and will have to resell this system.

Edit: I meant to include the wifi specs that my MBP is seeing...

IP Address: 192.168.---.---
Router: 192.168.68.1
Security: WPA2 Personal
BSSID: 1e:5f:67:58:65:9
Channel: 40 (5 GHz, 80 MHz)
Country Code: US
RSSI: -30 dBm
Noise: -89 dBm
Tx Rate: 1,200 Mbps
PHY Mode: 802.11ax
MCS Index: 11
NSS: 2