Thanks for the reply. I understand that there is no major difference in hardware other than that the XT8 has 3 radios of which one is used for backhaul. If two ASUS router are connected to the LAN which is then used for the backhaul, there is no major differences and standard routers could be better when they have more power CPUs and more memory. The Aimesh software is identical / similar between the routers.
It seems that the XT8 is a more fancy design at a much higher price.
Here are some links ASUS shared with me:
https://www.asus.com/microsite/AiMesh/en/index.html
https://www.asus.com/microsite/AiMesh/en/how_to.html
And below are the router setting location.
https://www.asus.com/support/FAQ/1035141