If I use all AP as a Mesh base with Ethernet backup. Is there any problem will occur?
Hello and welcome to the community.
You will need to designate mesh base and mesh client WiFi AP’s for meshing to work. For any mesh client, the wireless mesh connection will not esatablish if there is a wired connection. This will prevent a loop. If the wired connection is lost the mesh client will then connect wirelessly to a mesh base.
There are good instructions on how to setup mesh links here