Audio Volume Preferences: ReplayGain functionality

I have one album where various track volumes are noticeably different. I’d like to use ReplayGain to level them all out, but have a few questions about how ReplayGain is implemented in A+:
1.) In Audirvana Preferences/Audio Volume there is a “ReplayGain loudness normalization” option. Is this option invoked when the “Recompute ReplayGain” button is pressed for a given track or album, i.e., is it used to help generate the ReplayGain parameters, or is it used only for playback?
2.) Referring to #1, if the “ReplayGain loudness normalization” option is used for generation of ReplayGain parameters, how does each option affect the ReplayGain parameters that are calculated for each track or album?
3.) Referring to #1, if the “ReplayGain loudness normalization” option is used for playback, how does each option invoke the ReplayGain parameters, i.e. how is playback affected by each?
4.) For all of the other albums for which I have not computed ReplayGain parameters, do the “ReplayGain loudness normalization” options have any effect at all?

Thanks for any help.

The option in Audio Volume is to use the ReplayGain values computed in the tracks/albums when playing.
So you need first to get those values computed. That’s where the “Recompute ReplayGain” button is made for, or the Library>ReplayGain command of the File menu for batch computation.

The two parameters are that one uses the same volume leveling factor for all tracks of the same album, keeping the loudness differences among the tracks of the same album, while the other (per track) plays all tracks at the same loudness level.

Perfect. Thank you.