Sit back, twist the cable across, fight the pull.
Keep your chest lifted and rotate from the ribcage, not just your arms.
Sitting back in a V with your feet up while a low cable loads the twist puts your core in charge of two jobs at once, rotating against real resistance and holding the leaned-back position the whole time. Because the stack pulls from one side, you work each direction separately, and the cable's smooth tension resists you on the return sweep too, which a thrown medicine ball never does. It earns a place when you want rotation trained with actual load, not just fast reps.
Yes, and you should if the V position collapses your posture. Feet down makes the hold easier so you can focus on rotating well, lift them once your trunk can stay tall for the whole set.
Cables load the twist in both directions with adjustable resistance, so they're the pick for building rotational strength. The ball version is more about speed and reps, fine for conditioning, less useful for getting stronger.
You're twisting with your arms instead of your torso. Keep your arms long and think of them as hooks, the sweep should come from your ribcage turning, and if your elbows keep bending, lighten the stack.
