In short form... best to me:
Without discussing timing of the arm movement vs lower half.
* Break down, where you carry the hand doesn't matter to me, real low or less, just understand what that means to timing
* Elbow pull back behind back into scap, hand only slighly above elbow, wrist relaxed (not inverted W)
* Arm rotates up to 90 from side not around to second base
PS. I tend to believe that the harder you throw or the more you use mechanics that promote velocity, the more stress is put on the arm, so everything needs to be balanced with getting your body in condition.