The height and standard size adjustments are available from the side view. From the rear the up-down slider changes the width of the top part of the butt, and the left-right slider changes the width of the bottom part. cmar_EnhancedButtSlidersV3 adds the height adjustment from the side view and shape adjustments from the rear view.
I don't know of any such mods at this time. Changes in shape may slightly distort the patterns in some clothing. Changes in height of the derrière may cause distortion in some full skirts but it should be minimal. The effect is more noticeable in females for reasons that should be obvious. Affects male and female, teen through elder, both frames.
Adds more morphs to the EA butt slider, allowing adjustment of butt height and shape.