The Minis run their own apps.
You're overthinking it.
If it's connected directly to the router via ethernet, it's a direct connection. Even if it's connected over moca/coax, the moca network doesn't consume any additional bandwidth from the router. (In fact a moca network can save LAN bandwidth since moca devices will talk directly over the coax and not bug your router.)
Netflix's HD streams are only 5.7 mbps max.
It's television that is 12-18 mbps.