@Benjamin19838 

Is the exact model Archer C1200? You may check it by verifying it on the device's bottom label.

TP-Link currently only has some models that support EasyMesh, which allows you to connect the router to another EasyMesh router wirelessly to build a mesh network. You can read this thread to understand how EasyMesh works.

With TP-Link Onemesh, you can only connect the Onemesh routers together with their range extenders or powerline extenders, it cannot build Onemesh network with other brands. But you can still try to create the same SSID and password on the routers, then the client device will choose the one with a better signal automatically.