We are new to this, and trying to take advantage of existing ethernet wiring in our house to maximize performance of of the system, including wi-fi. 

We have fiber optic service to a modem. 

An ethernet cable from the modem's LAN port is connected to Port 1 on Deco X20, which is serving as the router.

An ethernet cable from the Deco router Port 2 is connected to a tp-link switch.

Ethernet cables from several wall jacks throughout house are also connected to the switch.

A satellite Deco in a bedroom is connected from its Port 2 to an ethernet wall jack (which is connected to switch).

A computer in that bedroom is connected to Deco Port 1 via ethernet cable.

Phones and tablets that roam get internet from wi-fi - from, presumably, the two Deco units.

We intend to connect another computer elsewhere in the house to an ethernet wall jack that is connected to the switch.

All seems to be working fine, but if someone with more experience than us has any observations about how we've set things up, or suggestions for doing it differently, we'd enjoy hearing from you!

Thanks!!