Hi chester,
The first thing I would suggest is to sleep on it for a while longer because one nights experience on a new mattress is not really a good reference point for any changes. The mattress layers will go through an initial break in period to some degree (latex less than other materials) and your body will also take some time (a few days to a few weeks) to adapt to a new sleeping surface. if you make changes too quickly then your body won’t have time to “catch up” to the changes and you could end up making changes too quickly and never quite getting it right.
I’m not quite understanding what you are hoping for in an additional layer though.
You mentioned …
but then you also mentioned …
Which says you are looking for a little more softness which is the “opposite direction” from more support (which comes from more firmness).
So I’m not quite sure what to suggest for adding more softness which would risk reducing the support (you would sink in more) depending on the type of support you mean (primary support holds up the heavier parts of the body and “stops” them from sinking in while secondary support fills in the gaps in the sleeping profile and helps maintain the natural curvature of the spine). The layers you have would be appropriate for your weight (30 ILD in a 3" comfort layer would feel softer for someone that had a higher than average weight) but perhaps you aren’t sinking in quite far enough in either your shoulders or hips for the foam under the small of your back/waist or ribs to come into firm enough contact with the mattress and hold up more of your weight. This could account for the need for a little more softness but would also lead to sinking in more which would fill in the gaps of your sleeping profile more effectively.
If this sounds right (and I can’t see you or know what positions you sleep in so this is only guessing) then I would suggest a little firmer layer than the 19/24 topper you are suggesting to account for your weight. I wouldn’t go below 24 for certain. I would choose the thickness depending on a more specific description of what “symptoms” you are feeling (and based on a little more time on the mattress to confirm them as a pattern rather than just an instance or two) and it would also depend on your sleeping positions. It would also depend on how much and where you wanted to sink in more deeply and where you didn’t.
Some sources for covers of all types (quilted and unquilted) are in post #4 here. The cover should fit the size of your mattress both in size (queen, full, twin, etc) and in thickness so all the layers can fit inside without “squishing” the layers too much. The material would be based on preference with wool quilting offering the breathability and ventilation benefits of wool but unquilted allowing a little more of the feel of the latex to come through. I would tend towards either cotton or a viscose/cotton blend (such as bamboo).
These are not “quilting” options (except the wool) but are materials you could add as a foam layer in your mattress (which I’m assuming is what you mean)?
Celsion latex (now called Talalay GKL fast response) does help a bit with temperature through heat conduction but Talalay latex is already very breathable and in combination with breathable quilting layers and covers and a breathable mattress protector and sheets … its not likely you would need it unless you wanted the absolute amount of temperature control possible. I would avoid Egg Crate polyfoam as a layer in your mattress or even as a topper unless you knew for sure that this was the only option you would be happy with. Wool would not be a comfort layer but you could add a wool mattress pad or topper or use wool in a mattress protector if you wanted more of it than was in your mattress cover (if it was quilted with wool). It will add some cushioning under the pressure points but won’t have the same full body weight distribution of a softer foam layer. It wouldn’t be as resilient or supportive under the 'gaps" of your sleeping profile.
I hope I answered what you were asking 
Phoenix