Hello, I purchased an AX1800 router a couple of years ago and HAD it connected to a different (NON-TP LINK) wifi extender. Just got a TP LINK RE315 extender today, added it using Tether, and everything seems to be working fine. The only difference that I can see---comparing 'before' and 'after'---is that I no longer have an option of 5G shown when I look at wifi availability with a device (such as Roku or Firestick). Previously, it would show my SSID and also SSID-5G-EXT.

Both my router and extender are listed as being compatible OneMesh devices, so I'm assuming I now have seamless roaming capability? On the extender, all 4 lights are lit, and in Tether, it shows the devices connected to the extender with each speed. I haven't noticed a problem yet, but with movable devices (such as a tablet), am I correct that the signal will use whatever is the best or strongest, as I move about the house? 

Anyway, happy with what I now have! Thanks!