This is definitely an area where you need to experiment and find out what works for you.
On an army cot, a swannie ranger folded into the bag's hood usually suffices. On the ground I need a bit of additional head and neck support and I'll often add a compact travel / camp pillow to the swannie ~ mine has a sleeve to hold a self inflating kneel pad which gives both added thickness and a bit of rigidity . If all else fails, I'll make use of a dry bag .
On an army cot, a swannie ranger folded into the bag's hood usually suffices. On the ground I need a bit of additional head and neck support and I'll often add a compact travel / camp pillow to the swannie ~ mine has a sleeve to hold a self inflating kneel pad which gives both added thickness and a bit of rigidity . If all else fails, I'll make use of a dry bag .