I am comparing a Tri-Band mesh WiFi against a Dual-Band mesh WiFi. A Tri-Band mesh WiFi system will be faster as the backhaul bandwidth is not shared. Yes, the difference in a router will be negligible but it is rather significant in a mesh WiFi system.
In a dual-band mesh WiFi system, the existing band will be reused resulting in halved the bandwidth.
Eg: Take the TP-Link Deco M5 for example as it is easier to explain. It is
AC1300 867Mbps + 400Mbps. The peak capacity of the second node is left up to 433Mbps due to halved bandwidth as it is shared with the backhaul. After considering interference, it will be around 250Mbps peak.

The Deco M9 Plus is AC2200 867Mbps + 867Mbps + 400mbps.
With Tri-Band will always able to deliver 867Mbps peak backhaul capacity as the existing radio is not shared for the backhaul connection. Resulting in 867Mbps peak capacity. After considering interference, it will be around 500Mbps on second node.
Back to the RT-AC86U twin pack. 5Ghz is up to 2167Mbps
On the second node, the peak capacity will be 1083.5Mbps.
On RT-AX92U twin pack. 5Ghz is up to 4804Mbps if you use the full 160Mhz Wireless AX.
On the second node, the peak capacity is 2404Mbps.
While these are just specs, the real world performance can only be displayed in testing and I tested all 4 models I mentioned above.

Backhauling using wireless looks nice to most people since you do not have to pull cable but the link speed gets smaller as distance go further, just like how fast your connection speed drops between your laptop to wireless AP. So, this is one of the reason the wireless mesh network can be slow. Putting each node closer to each others contradicts to the idea of having wide coverage with mesh. So, probably cable to each node still best choice for me