I can tell you how us classical guitarists hold it, I dunno about acoustic or whatever.
We rest the area right past our elbow at the much near the inflection point of the back curve or the top of the back curve. This is more about what is comfortable for you. You need to be able to slide it up and down to have a range of tones.
Then you keep your hand very relaxed and try to attack the strings at a right angle. Definitely do NOT put your hand against the body.
Fit your fingernails on the string, try not to put any flesh on it. Your fingernails shouldn't be naturally shaped, but more like a pick-shape...
Then,
for free stroke: when plucking the strings you retract the finger towards your palm with very little movement in the wrist or back of the hand. You don't want your hand bouncing up and down at all, which is a very very hard thing to do.
Vidovic has exceptional right hand technique (along with left hand)
https://www.youtube.com/watch?v=Nx7vOb7GNBg