Hi flexfit,
A pillow is a personal choice that has more to do with your own specific pillow “needs” and “preferences” than it does with the mattress you are sleeping on (although the firmness/softness of a mattress can certainly affect your choice of which pillow works best for a specific person as well).
For example side sleepers typically need a thicker pillow than the other sleeping positions because the distance between the head and neck and the mattress is greater and a thicker pillow is often needed to hold your head up higher and keep your head and neck in better alignment and reduce the pressure on your shoulders. Different mattresses can also need different pillows to keep your head and neck in good alignment as well because if you have a softer mattress then you will sink in more deeply and reduce the distance between your head/neck and the mattress surface that needs to be “filled in”.
There is more information about choosing a pillow for different body types, sleeping positions, and personal preferences and some links to other pillow topics on the forum in the main pillow topic here that should be helpful.
Phoenix