Firstly, we should connect the main deco unit to your internet with a cable connection.
In that case, we can put another RE unit in the room with the two devices.
And connect both of them into the Deco unit with cables to get internet.

Thank you, I think that answers my question. I will clarify what I am planning to do, and anyone else can jump in if I am incorrect about anything.

1. One Deco unit in my utility room will connect to the Fiber Optic connection running into my house.
2. A second Deco unit will sit on my desk in the room with the desktop and NAS device. The desktop will plug into one ethernet port and the NAS will plug into the other.
3. A third Deco unit will be placed elsewhere in the house.

This setup should allow all wireless devices in the house to connect to the internet via WiFi. It should allow the desktop and NAS to connect to the internet via wired connection to one of the Deco units. And it should allow all devices on the network (wireless and the wired desktop) to connect to the NAS device.

I am pretty sure this should all work. We will find out come Monday - that is when the Fiber Optic connection gets installed and the Deco system will come online!

I believe that both ethernet ports are active on a satellite M5 but I haven't personally tested that configuration.