RT-AX92U

I use aimesh without issue. 2 x rt-be92u. I also have an ax92u which was also a node. I removed that one as found didn't need 2 nodes. One router and one node. 10gb and 2.5gb ports. Use NAS with it. Also has dual WAN which was useful recently when ISP went off and used my iPhone 5g.

After trying Google Nest and multiple Tp-Link Deco devices, I always fondly look back at one Apple’s two devices - the AirPort Extreme and AirPort Time Capsule, which continues to work fine at my home. The only devices that appear to work without a hitch are the Asus ones. I’d recommend looking at Asus mesh systems like the RT-AX92U or ZenWiFi series. They work beautifully with wired backhaul, which you can now take full advantage of. What you’ll find good: actual web interface (no more phone-only nonsense), robust VLAN support for segregating IoT devices, proper MAC filtering, and ethernet ports on every node. Given your 2200 sq ft layout with that fireplace, keeping a similar node placement with Asus units should give you solid coverage.

Add another. I have 3 zenwifi bt8s, plus 2 old ax92u. 

With aimesh, getting them properly placed is key. If at all possible, they should all be connected to your single main router. I have 5 - 3 zen Wi-Fi bt8s and two old rt-ax92. I may add a third ax92, but I'm not sure yet.

I had Netgear (with an external firewall and generic access points) before they acquired Orbi, then tried Orbi which did not have enough info/options. Then went to at least 4 different types of AX Asus units for the longest time (10+ years with plenty of options and info but started to become unstable), then recently switched to Gryphon AX due to the need for parental controls for kids. I am thinking of going to Unifi next in a year or 2, as I miss the options/info that Asus provided, and get more with Unifi.

You can connect mesh nodes through Ethernet. OP has an Asus router, so they can buy more WiFi6 Asus Routers and connect them through Ethernet to set them up as AiMesh Nodes. My house network is set up like that, and I only have issues when streaming to my phone when going downstairs because it changes nodes, so it lags for like two seconds, and then goes back to normal. Other than that, it's a great experience all around.

It's called a wired backhaul mesh. Look it up. The point of using mesh nodes connected through ethernet is to keep the "seamless" transition between nodes without having any network degradation between them.