Best mattress for neck and back pain - A side sleeper

Myself 53kg (close to 9 stone), - Side sleeper – history of lower back pain and neck pain.
Husband 68kg – Back sleeper
Height: same at 163 cm
Using Heirloom mattress Benson Bed – Soft tension
Interested in Fusion 3 or Artisan Bespoke 004 or Artisan Luxury.
We first used Heirloom mattress Benson for beds on firm tension, but I felt stiff in the morning, however no back pain. So, we decided to change the mattress to soft tension. Now I ended up with upper back pain on some days and stiffness on hip. Didn’t have this problem before when I was on the firm mattress. I think the bed might be too soft for me. I asked this question before and I was recommended to get the Artisan Luxury with soft tension. But I wonder if this will be too soft? Because, my husband like firm mattress, I am used to the feel of Medium firm tension mattress, and I never had issues back then with standard coil spring mattress with medium tension.
I went to Heals to try Devonshire mattress – so that I will know how Artisan luxury would feel. I like it, as it is soft but very pillowy like cloud, almost like hugging you, but even with medium tension, I still feel that it might be too soft for me. I also think that my husband might not like it as it is very comfy, soft mattress.
I tried the Regal superb at Heals, and like it but feel like I am going to fall off the mattress when I sleep on the edge, Not great . you mentioned that you put firmer springs on the side of the bed, so I am sure this won’t happen to your mattress. Vi spring tiara superb is way too bouncy for me. So, Is Artisan bespoke 004 an option for me?
I tried the Tempur 22 medium tension in the showroom and I like how it takes the pressure off my shoulder , but I tend to get hot during the night. Even with pocket sprung, sometimes I feel hot but wont’ sweat, So memory foam is a no for me.
But Maybe I will be better off with Fusion 3 Latex Mattress? I will try Dunlopillo sovereign in the store to have a feel before I buy Fusion 3, As it is the closest mattress to Fusion 3 right? However , my worry is that I have an Ottoman bed with solid metal frame, there is no slate at all. I heard that this will not allow the mattress to breath, and might cause mildew and I will get hot during the night. Please can you help me to decide?
Thank you very much