Hi lisap,
Welcome to the Mattress Forum! 
There are certainly some very good companies there. As you’re already aware, I think highly of the members on this site in terms of their quality, value, service, knowledge, and transparency. I certainly wouldn’t hesitate to purchase a mattress from any of them.
The thickness of a mattress is just a side effect of the design. 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, but you may still “prefer” a mattress that is thicker or thinner depending on the design. There is more about this and determining your PPP in the Mattress Shopping Tutorial.
If you are interested a bit more in surface and deep support, there is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful as well. this may be a bit more technical than you desire, but you asked for a some more information! 
The next thing I would do is leverage the advice from the online retailers you are considering through a detailed phone conversation. A good online retailer or manufacturer will generally make suggestions that they honestly believe have the best chance of success based on the information you provide them when you talk to them on the phone because this is in both your own and their best interests but again … at the end of the day the only way to know for certain whether any specific mattress is a good match for you in terms of comfort, firmness, and PPP will be based on your own careful testing and/or your own personal experience so if you can’t test a specific mattress in person then the options you have available after a purchase to either exchange the mattress or individual layers or components or return the mattress for a refund (and any costs involved) would generally become a more important part of your personal value equation just in case a mattress you purchase doesn’t turn out as well as you hoped for.
Their detailed knowledge of their latex 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. The retail member of this site have great knowledge about component latex systems, and they will be able to provide you the best advice about the comfort you desire and the ability to achieve that with their different models.
I look forward to learning about your progress and what you end up deciding.
Phoenix