Wayne already covered the second part of your question. I’ll cover the first part. Logically 12FPS and on 2s at 24FPS should look the same, but the reality is it depends on the animation. If it’s slow to average motion a person may not notice the difference. With Faster motion it will look choppier. Side note: The choppier look is an artistic choice. That’s why the director wanted to do it in “Into the Spider verse”.
