3-Position Snatches or Cleans are a great way to develop technique and power. The goal of the athlete will determine in which order the sequence will be executed. By definition, 3-Position Snatch and 3-Position Clean is the execution of 1 rep from various heights on the body in a sequential order; such as floor, midhang, and the power position (hip).
Snatching or Cleaning from all 3 positions equals one repetition. As stated, depending on what the coach wishes to accomplish will determine which order they should be executed. If the aim is to develop power, the order should be (1) floor (2) midhang then (3) power position. The logic behind this by the time the athlete has reached the third position they should be under a bit more fatigue and executing a lift from the hips is challenging.
The athlete has no choice but to engage the legs & open the hips with maximal effort in order to be successful. Yes, this can be done with moderately heavy weight. In fact, the heavier the better so long as the athlete is successful in the final position. If however, the goal is better technique, then the order should be reverse; (1) power position (2) midhang then (3) floor. The idea here is that the athlete starts with the simplest of the movements, followed by the more complex movement from the midhang and ending from the floor for the full technique. This is similar to how coaches should teach Olympic Weightlifting; “high to low.” This video gives the example of 3-Position Snatch but the concept applies to 3-Position Clean.