Hi Awesome23,
You might consider getting a split mattress, so that you can customize each side separately. Being a side sleeper, and lighter, you’ll probably be wanting a bit more softness to let your shoulders and hips sink in a bit. As a heavier back sleeper, that softness would possibly be less suitable for back alignment for your wife.
If you’ve not already, you’ll want to check out Phoenix’s great post on how to find the right mattress for yourself. You can find it here:
https://forum.mattressunderground.com/t/how-to-look-for-and-find-the-best-mattress-for-you-read-first
I would think because of the sleeping style and weight differences, finding a mattress that has a suitable PPP (from above link) for you and your wife might be easier in a split mattress format (basically, each side of the mattress is customized separately). But whichever you decide, the first post gives you the tools to help 