Hi Bazinga,
EverEden is one of the Jeffco Fibers brand names and is still listed on their site and sold by a number of retailers. [EDIT: 5/19/17. EverEden is no longer listed or being offered by Jeffco.]
The choice between Dunlop and Talalay is a preference choice and some people will prefer one and some will prefer the other. There is more about the differences between them in post #7 here. Both of them come in a wide range of firmness levels although Talalay will tend to feel softer for most people than Dunlop in the same thickness and ILD.
There is more about the pros and cons of wool quilted covers vs knit covers that are more stretchy in post #6 here but this would also be a preference choice. Some people prefer the temperature regulation and less resilient surface feel of the wool quilting while others prefer the feel of stretch knit covers that has less effect on the resilience and contouring of the latex underneath them. The PLB mattresses have quite a thick fire barrier component that fits over the latex like a fitted sheet so it would tend to be less flexible and have a bigger effect on the “feel” of a mattress than other stretch knit covers that have a thinner and more stretchy fire barrier.
The component list here that I linked in a previous reply includes a list of the better options for zip covers I’m aware of and post #4 here includes the ones that aren’t quilted and are more stretchy.
As far as I know all of them have an inherent flame retardant layers (vs fire retardant chemicals that are added to the fibers after they are manufactured) but they would likely be thinner and have less effect on the latex than the fire retardant sock in the PLB mattresses but you can confirm that with each supplier since they would be more familiar with the specifics of the covers they sell than I am.
Phoenix