Hi Bachus,
Something that always fascinated me too, from the day I bought my Technics KN800 and realised the style tracks all showed up in my Notator sequencing software ( all except for drums, they came up as a program change. (duh! ) I was able to see what made up the various rhythms. See in notation form not have to hear it ( hopeless at that) can’t pick up by ear what the various instruments were playing.
So I basically studied them.
It’s basically about the rhythm because the notes in the various styles are the same, an arranger is only capable of using certain notes and transposing them correctly for the chords we play. ( Don’t know if I quite said that right. Haha)

As for picking styles to go with a particular song, I normally pick something that sounds good to me , might not be a good choice, but I’m only entertaining myself, so who cares.