@JoostVB Seems you are not aware that OneMesh does not support creating a mesh between two routers, only with router + OneMesh extenders.

So, you can setup your C6 as regular access point and set the WiFi as you please. But no OneMesh possible between your routers, TP Link does not support it yet. They don't support wired backhaul either.

@mocelet 

Ah yes clear, I see it in the description now. So basically i can setup my C6 as acces point (with wired backhaul) so I can get seamless roaming. Downstairs, when connected to the AX20 I should get the benifits of WIFI 6?

@JoostVB It is NOT supported, you cannot have seamless roaming with two TP-Link  routers. They will NOT create a mesh.

What you can have is two different networks, one upstairs and one downstairs. And the devices will choose the one to connect to, but moving from one to another will NOT result in a seamless roaming.

@mocelet 

Ah ok clear, thank you for your time. I was hoping seamless roaming was possible without OneMesh. Will be looking for another solution.

@JoostVB Well, there's roaming, but not seamless or hinted by the network as it depends on the device. Some (Apple products usually) may automatically switch to the better network if you move, others (Android based) will stay in the same even if there's a better one near and you will have to switch manually.

If upstairs there's no signal from downstairs, devices will connect to upstairs' router. But you will notice the disconnection from one and connection to other. In mesh system or at least network assisted systems you usually don't notice anything, hence the seamless.