Hi Rehabgal,
The ZenHaven does not come with a specific edge reinforcement system (this is common for most latex mattresses), and whether or not it is placed on the floor, and platform or a solid foundation would not change the characteristic of the “edge feel” of this product.
Most foam mattresses (including latex) don’t have or even really need side support if they have a support core that is firm enough and the comfort layers aren’t too thick and/or soft for the person sleeping on it (I know you have a specific need, so this isn’t necessarily the case for yourself).
There is more information about edge support with latex mattresses (or other foam mattresses) in post #3 here and in post #33 here but with a latex or latex hybrid mattress that is a suitable firmness level relative to the person sleeping on it then it normally wouldn’t be a significant issue for most people unless you often sleep or sit with most of your weight concentrated on the very outside edge of the mattress although the outside edges of a foam mattress would generally be softer than an innerspring mattress that has a specific edge support system, and I will admit if you are used to a very hard edge reinforcement system you do have to adjust your expectations when getting in and out of an all-latex mattress for the first few weeks.
The only way to know for certain whether the edges of a specific latex or other foam mattresses will be suitable for your specific needs or your preferences will be based on testing the mattress in person (or a mattress that is fairly similar) before a purchase or by actually sleeping on it (if you can’t test it in person before a purchase) and if you are uncertain whether you are one of the few that may “need” firmer edge support then a good return/exchange policy may be a more important part of your personal value equation just in case you are one of the few (generally in higher weight ranges) that needs or prefers a firmer edge.
I don’t know of any latex mattresses off the top of my head that have added edge support although there maybe a few that I’m not aware of or that don’t immediately come to mind.
There are quite a few spring/latex mattresses (hybrid) that feature innerspring units using firmer perimeter springs or foam edge reinforcement that may be of interest to you, and there are some of these listed in post #2 here. Additionally, most “traditional” innerspring mattresses will offer some sort of edge reinforcement, with firmer springs along the sides becoming more popular these days because of their ability to be compressed for shipping as well as their ease to be used on adjustable bed foundations.
Phoenix