Loudness Normalization is an effect that will level out your volume output to the same level like the -20db I suggested.
This way all of your sounds are the same level when played at the same volume setting so you can make them not too loud compared to other sounds.
Also what is notable is that the output volume should not be banging on the reds since when you play multiple sounds the mixer will overshoot and dampen and possibly break the sounds.
The Loudness Normalization IS the max volume setting ;)