Hi mikemc,
Welcome to the Mattress Forum! 
Latex is a component that is indeed very good at providing both comfort and support.
I believe you are referring to the members listed in post #21 here. They are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices. There are a wide range of latex options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency. While price is not necessarily an indicator of quality in the mattress industry, I think you’ll find when objectively comparing the materials contained within the mattresses offered by many of the members of this site to the materials contained within the mattresses bought by a few of your friends that the members here offer some outstanding values and the quality of componentry you’ll receive is much higher than the typical brands for a similar, or many times lower, price point.
Yes, Foam Sweet Foam is a member here, which means that I think highly of them.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else. Since you are a “big guy”, it is especially important that you have a configuration that will provide adequate support while still offering you enough comfort when you sleep upon your side, and the people at Foam Sweet Foam would be best able to offer advice as to what they think would work best for you with what they offer.
A high BMI does present special challenges and generally requires firmer materials (in the support layers especially). This could be firmer latex or innersprings (the type of support component would be a personal preference and in the right design either could be suitable) or even a zoned construction. The same overall guidelines apply with higher weights though that PPP (Posture and alignment, Pressure relief, and Personal preferences) along with using high quality durable materials that will maintain their feel and performance for longer periods of time (like the latex you are considering) are the way to make the best choices. Heavier people in general will need firmer and thicker comfort layers and firmer support layers than those who are lighter and because no materials will last as long with much higher weights the quality and durability of the materials and components is even more important than normal. I wouldn’t “rule out” any types of mattress and base your choices on your own personal testing. Post #3 here has more information and suggestions about heavier weights that is worth reading.
The 16" sample they mentioned would just allow a bit more “bending in” of the upper medium Talalay layer through the additional firm Talalay layer beneath it, which you might notice a bit more when sleeping on your side, but as they stated it wouldn’t necessarily be something that you’d need and I certainly would place trust in their recommendations whether you decide to go with a 13" or 16" mattress.
The thickness of a mattress is just a side effect of the design and by itself isn’t particularly meaningful because whether a thicker or thinner mattress would be better or worse for any particular person will depend on the specifics of the materials (type, firmness, etc.) and on all the other layers within the mattress. Thickness is only one of many specs that are used to make different mattresses that perform and feel differently and that makes a mattress suitable for one person and not another. There is more about the effect of thickness in post #14 here. Regardless of how thick or thin a mattress may be … the most important part of the “value” of a mattress is how suitable it is “as a whole” for your particular body type, sleeping positions, and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) regardless of how thick it may be. There is certainly no reason that at your weight you would “need” more thickness than either of the mattresses you are considering but you may still “prefer” a mattress that is thicker or thinner depending on the design.
I would definitely have a detailed conversation with Foam Sweet Foam before making a final purchase decision.
While I can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either a mattress or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
As you can read from my comments above, I certainly would trust the guidance offered by a reliable manufacturer or retailer. Their detailed knowledge of their mattresses and how they fit with different body types and sleeping positions along with your feedback from local testing, a customer base of many people that they can use as reference points, and any exchange, return, or any options they have available to customize a mattress after a purchase can help lower the risk of an online purchase. These online retailers or manufacturers can also be a good “value reference” for local purchases to make sure that if you are paying a “premium” for a local purchase (in exchange for the kind of “in person” guidance, service, and value that comes with dealing with a local retailer that can help you make more “accurate” choices that you have tested in person) is not too high. And the good thing is that Foam Sweet Foam has a 60 day comfort exchange program and a 120 night trial period, in the unfortunate case that your purchase turns out not as well as you had hoped.
Subject to first confirming that any retailer or manufacturer on the list that you wish to visit is completely transparent (see this article ) and to making sure that any mattress you are considering meets the quality/value guidelines here … the better options or possibilities I’m aware of in and around Henderson, Texas would be the Shreveport, LA list here. Unfortunately, I didn’t find anything of quality in Henderson. I did find a few more stores in Tyler but nothing that carries latex products. Your closest best bet would be the Dallas/Ft Worth list in post #4 here , but I know that is a bit of a drive for you.
I’m interested to learn what you’re able to find out and end up deciding.
Phoenix