[1] Pullovers can be made to affect either the chest or the back depending on how wide the grip is (barbell) and the position of the shoulders.
A research done on the pullover movement using a barbell suggested more effect on the pectoralis major muscle as compared to the latissimus dorsi.
[2] A typical pullover involves resting the upper back on a flat bench.
Keeping the hips off the bench is said to help in balancing the weight and stability during the movement.
In this variation the weight is lowered till the upper arm is in line with the torso.