Victoria
Frankly, you can’t go wrong either way.
My wife and I had been the same 500 lbs as the two of you.
We home tested the Simmons Beautyrest Black/Latex Topper combination.
After the 4 years we had it, it remained in like new condition.
Our Son and his wife, (not small people) have had it for 4 years.
After 8 years, it’s still in like new condition.
For the past 4 years, we’ve been sleeping on a Natura of Canada Greenspring Ultra Plush.
Again, it’s in like new condition, these 4 years later.
Both use a pre-compressed, individually pocketed coil system.
The Natura Greenspring has a higher coil count and the steel used is stronger.
Rolling together is not possible in this type of mattress.
Normally, I would leave it up to you, as to which one.
However, you’ve complicated the issue with an adjustable bed base.
When you’re in bed, watching TV or whatever you’re doing that requires the head to be raised, your body weight shifts from being evenly distributed to concentrated at the point in the mattress just under your butt.
The stronger Natura Greenspring coils will wear better.
The Pure Talalay Bliss Natural Talalay Latex Topper is the one I recommend.
2” Plush is all you need for the sake of added durability.
The 3” Plush is noticeably more comfortable.
We, recently, changed our latex topper from 2” to 3” and, WOW!, what a difference!
The 3” is no less than wonderful.
Here are links to both mattresses and topper.

Simmons Beautyrest Black Pricing at a Glance . All Mattresses are Freshly Made to Fill Your Order. Approx. Delivery Wait Time: 2 Weeks. White Glove Delivery Includes: Set-Up in your Bedroom, Removal of the Old Mattress, All Packing Materials Removed. Delivery is Free and There’s NO Sales Tax.
themattressexpert.com
|
https://themattressexpert.com/natura-greenspring-pocketed-coil-mattresses/

The Natura GreenSpring series combines the natural elements commonly found in Natura, such as wool and latex, but it has a specially designed pocketed coil system to provide your body with extra support.
themattressexpert.com
|
The latex topper arrives via UPS.
Delivery is free and there’s no sales tax.
I also suggest using a waterproof mattress protector.
We have one made of organic cotton, which we use at home.
Perspiration, more than anything else, will seep into the upholstery material.
Keeping your mattress clean and dry will maximize the comfort life of the bed.
Shown here:

Our fitted sheet style mattress protector is designed to be undetectable under your fitted sheet. First, we started with an incredibly soft 100% GOTS certified organic cotton jersey sleeping surface.
themattressexpert.com
|
Phone: 1-856-874-6894
Email: themattressexpert@live.com
Website: http://themattressexpert.com/
Factory Direct to You….
All Items Made Factory Fresh to Fill Your Order
Free Delivery Nationwide….NO SALES TAX.
IMPORTANT INFORMATION:
Protect and maximize your mattress investment. Use a waterproof mattress protector.