Which devices to connect (or not connect) to Orbi Satellite ethernet ports?

I have not ever used a DirectTV DVR, but I assume it needs or would benefit from an internet connection greatly, as would the 4K TV, if just for firmware updates.

If the TV, DVR, and Xbox One S are going to be near the Orbi Satellite, I would definitely use their wired ethernet port connections instead of using wireless for such a short distance to the satellite, which could cause interference.  Taking 4 devices that could use WiFi in a small area and reducing it to 1 device is always a good thing. So if they have ethernet ports, use them.

It seems that your placement of the Orbi Satellite is more device dependent (where all the 4K goodies are) than coverage dependent (trying to provide more coverage past the edge of current useability), since Wifi is working pretty well in the house already.  In this scenario, I would be cognizant that I might need to turn down the transmit power on the 2.4 ghz channel via the Orbi router menu so the wireless signals aren't stepping all over each other, especially as Orbi Router and Satellite use the same channels for talking to client devices.  You might want to start at 50 percent power and go from there.  This does NOT change the power of the backhaul signal between Router and Satellite, so don't worry about that.  I have not had to drop the transmit power of the 5 ghz channel in any of my scenarios, but if the satellite ends up fairly close to the router, it could be a consideration,