Does the Apple TV need to stay on after it is set up?
Does the Apple 4k TV need to stay on after it is set up?
Question marked as
The sleep functionality sets it to a low-power state (standby), where it will listen to remote power-on and network power-on.
Sleep or wake Apple TV - Apple Support
To have it truly turn off, you can disconnect from power. Not needed, and a bit inconvenient. Your setup will be retained.