Two. One classic one and a specific rectangular neck position pillow. I had used only one pillow for years until i met one of my ex. She had around 7 pillows around her bed and used them aplenty, almost as she never wanted to touch the actual bed surface with her head.

1? Why do you need more?

One and it's got to be pretty flat. Pillows in hotel rooms are so puffy, I can never sleep properly.

1 and it is a cube.

Depends on how thick/firm they are. My bed currently has 2 thin/soft pillows that sit between my head and the wall, plus one extra firm pillow between my head and the mattress.

I have the flattest buckwheat pillow and it's perfect.

I used to have 3 but switched to 1. Makes my back and shoulders feel a bit better since my neck isnt so high anymore.

Two. One hard and one squishy soft. Makes it easy to flip around each one and reach the right density and heft.

Two, both are quite firm

1
I have a pillow from Tempur (hard when cold, very soft when warm).
Upside: Pretty thick. About 8-12cm

beans