Set shot is when your feet don't leave the ground. Jump shot is when ya jump.
One-motion shooters (think Steph or Harden) definitely don't jump as much, because they are using their legs more effeciently in the shot. They shoot on the way up which means they use the full power of their legs. A one-motion shooter can put it up from 2 steps beyond the arc without changing much in their hands.
Someone with a two motion shot (Ray Allen, Demar DeRozan, Jordan) jump really high to shoot but end up releasing the ball on the way down. What that means is to shoot farther, you have to push harder with the arms, because the legs are less involved in the actual push of the ball. The advantage being, or course, that the release can physically be much higher to elevate over defenses in the mid-range and when closely defended on the 3 pt line.
In today's game with such wide spacing, that elevation becomes less important. Players just shoot farther away, and more accurately. Shooters have a ton of time to unload, it's just much deeper than in the 90s and 2000s basketball.
The theory on shooting has changed A LOT in the last 5 years with the advent of 3s being so important to the game. A good coach is not going to teach many people to shoot with a two-motion shot, because coaches don't value elevating over defenders like they used to.
