@cheeseburger467 

If you plan to use Ethernet backhaul for X20, that won't slow down your Deco mesh. As long as you can have X20 wired in such a way it can use Ethernet backhaul, and your networking gear supports it. See this discussion: General questions about Ethernet Backhaul feature on your Deco

In general, even connected wirelessly X20 won't impact your entire home WiFi performance: devices connected to X20 might get slower speeds than those connected to X60s, but devices connected to X60s won't see their speeds reduced.

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Hint: if you don't have any other Satellite X60 wired, and unsure if your home networking gear can support Deco Ethernet backhaul, take one of Satellite X60 you have to where you plan to place future X20, wire X60 there and see if it uses Ethernet backhaul. If it does, your X20 will, too.