XG1v4 Streaming Video : Internet/Network or Coax?

For the past 11 years, up until today, I have been using a Tivo DVR (most recently a Roamio). Due to Comcast discontinuing VOD support for Tivo, as of today, I switched over to an Xfinity XG1v4 Comcast DVR. I went with the XG1v4 because I have a 4K HDR TV (like most everyone else these days), in addition to thinking that this is more current/up-to-date electronics than the X1 DVR box. 

I've got it all hooked-up and activated and it seems to be working just fine watching live TV, recording, playback, etc. I now need to play with the Apps a little more (Netflix, YouTube, etc).

By "I've got it all hooked up", I mean completely hooked-up, including the gigabit Ethernet ... which brings me to my question: What interface does the Apps streaming data come from? the Cable Coax, the Ethernet Cat5, or WiFi? I have not found any menu on the XG1v4 DVR that lets me setup the network interface. This leads me to believe there is no network interface to this box, ie it all comes from the Coax.

How does this compare to the standard X1 DVR -- does it also do its streaming to Apps using data only from Coax or does it come from the home network? If the XG1v4 truly is getting all internet data via the Coax, how does the available bandwidth for streaming compare to a DVR (eg Tivo or standard X1) if those boxes get their streaming data from the home network? If I want to stream 4K UHD video from Netflix through the XG1v4 how well does the Coax support this, ie what is the sustained bandwidth I can expect? My Comcast plan includes Extreme Pro Ethernet along with my Motorola MB8600 DOCSIS 3.1 modem and Netgear Nighthawk R9000 router I am getting 600 mbps downlink. How does that compare to the Coax?