The AX88U Pro is indeed an odd product because the main new feature, VLAN, is only available in the beta software. I bought this router mainly because of the VLAN feature. I was thinking going all the way and buy a unit that I could install pfsense on and use the other wifi routers I already have to set up 2 different wifi networks. Now that AX88U Pro had VLAN I thought the smart thing to do was to use the VLAN feature on that router and at the same time get a new wifi router that I could incorporate into a asus mesh network. EG create a mesh network with AX88U pro as the main router - use AX86U as a node for the main network - both cabable of creating a 2.5 GB with ethernet backhaul. And from the AX88U pro use the VLAN feature to connect to another an AC86U, and from this router create another mesh network with another AC86U - all with ethernet backhaul. Then I would have 2 different truly separated (mesh) networks all connected with ethernet backhaul. The main mesh network (AX88U Pro + AX86U) would consist of all my main computeres related to (home) work etc - the second mesh network should be a IOT network and for my children and friends to use. I've always used merlin firmware, but as merlin always use a stable version - his latest firmware does NOT have the VLAN feature of the AX88U Pro. I find it a little bit frustrating that Asus is selling a feature, EG VLAN, that has to rely on beta software to work.
That said - I do hope Asus soon releases a stable firmware version for this router that has VLAN - and that Merlin will follow up with a release. My test so far regarding wifi coverage and speed with my AX88U Pro against the AX86U seems to be very similar but not 100% on par with clients using only AC network. I really don't know why, but maybe it could have something todo with beamforming that I do no longer see as an option in AX88U Pro with the 5GHz band? So right now it seems that I got a new router that has a little bit worse speed for AC clients than my AX86U,and that the stable firmware on AX88U Pro does not bring anything new to the table like true VLAN. I have very few AX devices - so I did not speed compare the AX86U vs AX88U Pro - only AC clients was tested. And I feel I do have to mention that my old AX86U based mesh network was fine tuned - and I've not have the time to fine tune it with my AX88U Pro as the main (mesh) router. So the small performance degradation I see against my former AX86U based mesh solution with AC clients may disappear in time as I start fine tuning all the settings..