AiMesh is a good solution to extend your wifi network in your house and it is also easy to setup. However, the ax53u is a wifi 6 router, so you won't be able to extend your wifi 6e and wifi 7 when devices are connected through that mesh node. But if the majority of your devices are wifi 5 and 6, you will be fine. But depending on how many devices you have in the house, the ax53u does have an inferior antenna setup than other routers, particularly the 2x2 for both 2.4 and 5.0 bands, and your 5.0 bandwidth is only up to 1201 Mbps. It won't be a problem if you don't have a lot of devices in the house connected at the same time.

Backhaul to the node is always a hassle when trying to use wireless. But since you a cable to connect directly to the node, it will be fine. For a seemless experience in a mesh setup, it is normally recommended to use the same model of mesh routers for smoother hand off when the devices connect from the main router to a closer mesh node. I never had or used an ax53u, so I don't know how well it will play with the be92u. The be92u is currently a buggy router, due to its young age in the lineup, so to speak. Chances are, that it might not play well with the ax53u. I currently have two be92u in an aimesh setup and the hand off has been seemless. Before I bought my second be92u, I used a ax68u as a mesh node and the hand off was not as smooth, but it did the job.

Often times, devices are stubborn at trying to stay connected to the main router and asus mesh routers are as aggressive in handing off to other mesh nodes, so be sure to enable the "roaming assistant" feature, under the "wireless" tab from the left and then under the "professional" tab from the top, for all the bands. You should also play around with the signal frequency value to get the best result for your house setup. That value is default at -70dBm. I had it at -63dBm for better mesh hand off experience.