Just my idea.
Let's throw away this term of "style" that means nothing.
There are 3 throws. More or less vertical overarm, more or less vertical underarm and more or less horizontal.
There are 3 starting positions for the slingstone. Held in front, hanging on the side and held behind you.
From there, test what suits you. With (1 or more) or without slingstone rotation.
Spin control is only used for control a dreamlined projectile.
After, there are local specificities : old indian, very long sling  in the island of Pacific.
The styles of "double feedback rifle style generated with delayed release" for me mean nothing. 

Just my idea.