Side sleeper or back sleeper — does the pillow shape matter?

Yes. Across reviewer testing notes, side sleepers generally need a higher loft to fill the shoulder-to-ear gap and keep the spine neutral, while back sleepers do better with a lower center and a defined neck-support roll. Pillows with dual-height contours (a higher side and a lower side) or adjustable inserts handle both positions better than single-loft designs.