Hi Dormir,
Welcome to the Mattress Forum! 
I’d recommend to do some personal testing if possible and avoid as much as you can what I call “theory at a distance” so you have a reference point for how the different core combinations feel and perform for you both. There are just too many variables in both body type (at the same or different weight) and sleeping positions (there are many more combinations than just the three basic types) and personal preferences involved to be able to use specs alone to predict with certainty what any specific person will do best with.
If you do choose to make a purchase based on “theory at a distance”, then I would go with the suggestions of the manufacturer or retailer you are working with. TMASC is a site member here (which you may already know) which means I think highly of their products, knowledge and the advice they provide. They will use their knowledge of their BE mattresses along with the more detailed information that you can provide on a phone call or a visit (about your specs, mattresses you have tested or are used to, and your preferences) to make a suggestion based on their best estimate about which of the BE mattresses will likely suit you best. Their advice will usually be fairly accurate for most people, even a bit higher BMI, but the ability to change the layering and/or their return or exchange policies can play an important role in your decision as well. The latex used in the BE mattresses is a high quality and very durable material.
With heavier weights … the odds are good that you would need both firmer comfort layers and support layers, and perhaps slightly thicker layers as well. As a general rule, 8" or so of latex is a good place to start for slightly higher BMIs, but everyone varies. Your sleeping position will also enter into this equation, with side sleepers generally having a bit more of a need for conformation. You can read a little more about the potential benefits of a thicker mattress or sleeping system for heavier weights in post #14 here . If you go with a thinner mattress (8" of latex) and find that it is not sufficient in support, you always do have the option to add a latex topper down the road, but I would have a concern with having a support core that was too soft, as you want to make sure to defer toward alignment first.
All of this is just some of the variables based on “theory” or “averages” rather than being based on your personal experiences though which may indicate something different and will give you a much more accurate reference point. There are usually several different combinations that will provide you with the PPP (Pressure relief, Posture and alignment, and Personal preferences) that would work well for you. Post #3 here has more information and suggestions about heavier weights that is worth reading.
The best guidance I could give you isn’t “specs” at all (this is always best coming from the manufacturer/retailer of specific mattresses who can give you suggestions for their designs and the options they have available) but to encourage you to spend some time testing latex mattresses locally or at TMASC. Again … I would personally never use specs alone to make a choice without some local testing as a reference point unless there were no other options available to me.
I’ll be interested in learning about any decisions you may make and the results of your conversation with TMASC and any testing you’re able to perform.
Phoenix