With more ISP's creating data caps, I'm curious how much data will be used if you shut your TV off, assuming your Chromecast is plugged into the wall outlet as opposed to the USB on the TV. If you're watching YouTube TV and go back to the Google TV home screen does the stream to YouTube TV pause?
Well, going to home screen will stop the stream, but shutting the TV off, alone, going to depend on the HDMI-CEC data sent by the TV, so i wouldn't rely on that without testing it. This said, pressing power button on the CCwGTV remote shuts both the TV and the CC off by default.
The thing i'd worry slightly more about, that was always an annoyance on a regular CC, is ambient pulling photos and using data for no good reason, not really that big of a deal, but 24/7 it does add up. CCwGTV doesn't have to use ambient, thought, you can setup any screensaver app you want instead.