@HerbertV Thanks Herbert for your reply, glad to hear that you figured it out finally. For the negotiation speed of the LAN port, you can refer to https://www.tp-link.com/support/faq/2427/ And you...

@Unrlx Thanks for your reply. Please keep us posted once you came back home and verify the network connection. Good day.

@izzfaris Fast roaming won't turn it on automatically, you need change it manually. You can turn it off to connect the devices to the Deco wifi network first and then you can turn it on and verify...

@ragnakore You can change one of the Deco in Diagram 1 to the router mode, while to build up the mesh network together, the 2 slave Decos should be wired to the main Deco, not the modem router,...

@jonnyv Thanks for your updates, glad to hear that it works as expected now. Generally speaking, once you enabled QoS and set it up, it will take effect within seconds. For the latency issue, cause...

@tomhawkson1990s Is modem a pure modem or is it a modem router? Cause you switched the Deco to AP mode, as my knowledge, the modem should be a modem router which you can get internet from it...