Background: I want to redesign my home network. It's a two-story concrete house with network cables running from two hub points to rooms on that floor. The hubs have a network connecting the two.
Long story short: I have two xiaomi ax1800 units that I want to use for serving wireless network for each floor. The infrastructure will be handled by a separate nanopi r2s unit with openwrt that will serve as dns, dhcp e.t.c. So the ax1800 units are needed only for the wireless access.
The question is should I try and connect them as "mesh", or should I use them in "access point" mod? From what I see, the default configuration blocks all mesh options when running in access point mode.
Sorry for text only version, I am writing on a phone.
So as long as I am using wired backhaul there is no difference? I am looking for as seamless roaming experience as possible, since both APs will have the same SSID.
Roaming and fast roaming are supported more than 10 years already. The difficult part is the fine tuning to force the clients to disassociate and associate, but this is irrelevant to mesh or no mesh.
'Mesh' is the latest buzzword, touted by the vendors - but it actually means very little (and what it means differs quite a lot between different vendors, as basically none of them implements IEEE 802.11s and rather goes for their own proprietary approaches that can't interoperate with other devices.
If you can wire all APs, you should do so, as this will provide by far the best results. With an all-wired backhaul network, the term mesh loses most of its value - as it isn't needed anymore. It's nothing else but a network of hardwired APs, providing the same network and at best dabbling into 802.11k/v/r territory (similar to what luci-app-dawn aims to do as well) to some extent (in practice many do not, because some clients really don't like 802.11r). The only real advantage of mesh solutions with a wired backhaul, would be the central configuration (changing settings once, on the mesh router, than having to log into each AP and changing options individually) - functionally, for the participating wireless clients, there is no real difference between purely wired-APs and a proprietary mesh system.
If you do need a wireless backhaul for some APs, but have those mounted rather statically and don't move them around on a whim, WDS/ 4addr can provide the same functionality as a mesh solution - what meshing solution can get you here, is the convenience factor of being able to dynamically move APs around (this is the only aspect harder to implement with OpenWrt) and have them adapt to finding a different uplink (5 GHz --> 2 GHz, wireless to wired) by themselves. While this may be convenient, it's usually not that necessary in a typical domestic (and even less commercial) setting, as one will usually leave the APs alone - once they've found a good place to be.
While meshing as an idea would theoretically imply the ability to load-balance between multiple uplink routes, basically no commercial mesh implementation actually provides this feature (OpenWrt can, as e.g. the Freifunk deployments prove on a large scale basis), so no - aside from the convenience factor of central configuration and dynamic adaption to changing uplink conditions, there is no advantage of using a mesh system compared to (OpenWrt-) APs.