Had to laugh at the feather pillow, had a bad experience with these and found out that I'm allergic to the feathers, unfortunately after I had bought a very expensive duck feather duvet, this was in the 1980 s when they were fairly new on the market. Lol.
I pile all my cushions and pillows up and have a bolster cushion on top, hook one leg over them, this really helps the pain in my back and legs and often takes it off altogether so I can sleep. I did buy a pillow designed for sciatica from the disability shop but because I'm small it was too high for me but would work better for someone of a more average height. I basically do the same thing with my pillows but can adjust it to my height. Finding the right position to sleep in really makes a difference. X

Ghost pillow. (I got them on groupon at a decent price) i love them.

I use a "my pillow" which allows me to adjust it with a hollow center and adjust the amount of support under my neck. I'm all fused, mechanically from broken neck from C-4 to T-2, all of T's from AS and all of L's as well with less than 15 deg. flex in total. I do tend to sleep on my side or back for CPAP use with sleep apnea brought on from the AS fusing ribs and Thoracic - Cervical regions of spine.

I find I need a pillow that has chunked or adjustable fill (buck wheat husk is good too, Japanese style) Feather fill is good, old fashioned, and comes with getting stuck by quills occasionally/nightly.

I have a pillow between my legs, another to support my right shoulder which subluxes a lot. These are both latex. At the top I have two fibre pillows and two feather pillows which I arrange to the most comfortable position for my head and neck every night.

I'm getting an adjustable bed soon, I'm wondering if there'll be any room for me in it!

I went without a pillow to retard the curling from AS. My progression is such that I do have forward head and went to standard pillow to prevent neck injury. I did try some of the ergonomic pillows but they were no good , as my neck has some fussion . I do use tens/ems to relax muscles and sleep better. Bad nights I use some CBD cream .

Not what you asked but it's all I got.