Hi pracies,
You can read a little more about “organic” latex here. There is only one company that makes certified organic latex at the moment and I personally question whether the certification is worth the extra money. In most cases, mattresses that are sold as being “organic” are really only talking about the wool and cotton cover. All the better quality latex (blended, natural, and organic) you will encounter has passed the same Oeko-Tex standard 100 “safe for babies” certification for VOC’s and harmful ingredients or from similar testing organizations. I also know of many people who suffer from MCS who were pleasantly surprised to find that they were fine with even blended Talalay latex even though they were expecting that it could cause issues for them.
Of course there are many people who believe that an organic certification provides a level of assurance that they are willing to pay extra for vs 100% natural Dunlop that is essentially the same material but in the case of latex where the Oeko-Tex testing protocols are quite stringent and from a purely “safety” point of view only I’m not so sure that’s valid.
The mattresses from mattresses.net do have the single piece which doesn’t have the same design flexibility as two 3" layers but as you mentioned once you have a final configuration with latex layers it’s rare to adjust them anyway and with children it may be less important yet. SleepEz has several versions of multiple 3" layers for those that are looking for this feature but at a lower cost than Savvy Rest.
I would make the same firmness choice with a single layer.
I hope this has helped.
Phoenix