“Sound effects” & “Dolby Digital”

I’m going to use an obsolete Apple TV 3rd generation as a music streamer from my iPhone XR to my stereo via Airplay.

1. In the setting menu, there’s “Sound effects” function which allows to select between On and Off.
2. There’s also “Dolby Digital” which can be select On and Off as well.

I wonder what the responsibilities of these two functions are.

Note that I ONLY use it for music purpose, never use it for video or movie streaming.

What is the best setting for these two functions “Sound effects” & “Dolby Digital” for music purpose?