I have a reasonably new pocket sprung double bed in which I sleep alone it’s super comfy. Why don’t you buy single beds then you can both choose exactly what suits if they don’t match who cares as long as you both get a good night.
when I had my first knee replacement, our very high SuperKing size bed was impossible post op. So we moved to another room which has 2 small doubles and we each had one. And later when I had recovered, we decided to stay in that room, with en-suite- and put the two beds together, so a 2m80- or 8 ft bed- sheer bliss. Just bought two new mattresses.
When I was married we had an American king size bed. I still have a large double, to myself now. When I stay at my blokes (not at all since first lockdown) he has an average double. It isn't big enough and I don't sleep well. The only person I want to share my sleep with now are my DGS when he has a nightmare.