Hi Joeboo80.
Welcome to our Mattress Forum. 
You are not the first (nor will you be the last, I imagine) to report pain on a Purple Mattress. The comfort layer on the Purple Mattress is buckling column gel, which is frequently too firm for people unless you happen to have extreme support needs. That said, there have been a number of complaints with pain associated with a lack of support on a Purple mattress as well.
Unfortunately, this isn’t something we can say for sure as it really comes down to your PPP (Posture and alignment, Pressure and relief, Personal preferences).
As you mentioned you are a taller, larger sleeper, something to consider is a thicker and softer comfort layer may be necessary to allow your shoulders to sink in enough. But, your wife is quite small so very likely has different comfort and support needs than you do.
Also, to factor in durability for someone of your stature, if you’re considering memory foam or polyfoam mattresses… for polyfoam, I would look for 2.0 lb per cubic foot density in these materials (or higher.) If the mattress is two-sided then I would use a minimum foam density of 1.8 lbs per cubic foot or higher. Memory foam (or gel memory foam): If your mattress is one-sided then I would make sure that any memory foam is at least 5 lb per cubic foot. If the mattress is two-sided then I would use a minimum density of 4 lbs per cubic foot.
Now that I’ve mentioned that bit…have you and your wife considered a split configuration? If you pick a split configuration, you can get the support and comfort each of you prefers. A number of our Trusted Members offer split configurations. Also, they are extremely knowledgable and compete with the best in the industry. If you present them with your sleeping specs, comfort/support needs, etc. they will be able to help you choose the best fit both product and ILD wise…whether you choose a split configuration or not.
Off the top of my head, I would suggest exploring options with the following…
Arizona Premium
Sleep EZ
FloBeds
Latex Mattress Factory
Nest Bedding
You mentioned Ghost Bed’s Flex mattress. What is it that calls your attention about the Flex? Is it a question of comfort, durability, or something else?
As an FYI, the customer service at Ghost Bed is great and if you approach them with your sleep stats and questions, they’ll be able to help you decide whether the Flex is an appropriate mattress for you.
I realize I’ve thrown a lot of information at you here. I hope it helps point you in the right direction, and of course if you have more questions, we are always here to help!
NikkiTMU