I got the small size, which is perfect for this type of pillow. Typically I don’t like a big, firm pillow, just a bit to keep my neck straight. The buckwheat is firm, but it can be molded around your neck and head the way you like. I had to play around with the amount of buckwheat filling, trying less, then more, then less, etc. I seem to like it somewhere between 1/3 and 1/2 full. By that, I mean if I hold the pillow by the zipper end, the buckwheat flows to the bottom of the pillow a bit below the halfway mark and the top portion is empty. Too full, and the buckwheat flows less easily and it starts to feel too hard. So if you think it’s too hard, remove some of the filling and see how that feels. On the downside, it looks rather deflated on the bed, lol!
Usually I pull the pillow to mostly go under my neck. If that’s not perfect, then I push my head in a little. Sometimes I’ll just take my fist and punch a little hole for the back of my head. It’s like sand in that way, will stay the way you form it. When I change position, it usually adjusts with my movement. If not, I either use my hand to reform the shape or I give my head a tiny turn or two to dig in.
Have not gone back to a regular pillow for sleeping, but having fluffy ones for looks might be a good idea if that is important to you. If you get the small size, I suggest you look for a video online to show how to put it in a regular pillowcase so it fits perfectly and looks really nice (and less deflated!). I put mine in sideways which works well.