I have a NAS, but it's old. Perfectly good as a backup though, so I keep the pi in sync with it.
As for the pi, it's connected straight to the TV's HDMI. It has a 7.1 USB audio that connects it to an ancient Yamaha receiver. I have no other media sources, and the TV is one of those digital signage models that has no smart features or tuners. So there's nothing complicated to do really. The Pi puts the screen to sleep when there's nothing playing.