The video shows the differences between a raw spectra of lactose (where we can se high differences due to the particle size). After applying SNV those differences almost disappear.
If we combine SNV and Second Derivative, we increase the resolution but the effect of the particle size is also take it out due to the SNV part, but we see an improvement in the resolution.
In case we only apply the Second Derivative we increase the resolution and keep the particle size effect.
All these combinations help to find the best option for a quantitative or qualitative model.