Hi Miserably Melting,
There is more information about wool toppers and how they compare to various foam toppers (at least in very general terms) in post #8 here and in posts #3 and #6 here and there are some additional comments about wool toppers and a list of some of the better sources I’m aware of in post #3 here.
While it’s not always possible to to track down temperature regulation issues for any particular person on a specific mattress because there are so many variables involved (including your room temperature and humidity, your sheets and bedding and bedclothes, your mattress protector or any mattress pads you are using, and where you are in the “oven to iceberg” range) and some people can sleep warmer on mattresses that most people are generally fine with … there is more about tracking down a potential cause or causes for temperature regulation issues (at least to the degree possible for a specific mattress) in post #2 here and the posts it links to that may be helpful (including more information about the wool fleece toppers vs toppers that use wool batting).
Your mattress protector could also be playing a noticeable role in your sleeping temperature and there is more about the pros and cons of different types of mattress protectors and some examples of each of them in post #89 here.
Other variables that can affect your sleeping temperature besides the mattress itself would be the type of sheets you are using, your blankets, your room environment, and the bedclothes that you sleep in.
If all you are looking for is additional temperature regulation then a wool quilted mattress protector or a relatively thin mattress pad (in the range of an inch or so) would usually be enough but I would keep in mind that memory foam (or gel memory foam) can sleep warmer for some people than other types of foam materials … even with a wool topper. The only way to know for certain whether any mattress protector, mattress pad, or mattress topper will be “temperature regulating enough” for you will be based on your own personal experience because some people can sleep warmer on a mattress/topper combination that other people would be fine with.
Wool will compress by about 30% of its thickness as you sleep on it over time and this will happen faster in the areas you sleep more often or under the heavier parts of the body than it will in the areas that you sleep on less or under areas of your body that are lighter. It will tend to even out over time as you spend more time on the areas that you sleep on less often and they “catch” up to the areas that you sleep on more often over the course of the first few months (up to about 6 months or so) but it shouldn’t have a significant effect on the comfort or support of the mattress. I would make a point of sleeping in different areas of the mattress initially and also rotating the topper from time to time to help with the process.
If a wool topper can be washed (and many can’t) I would also make sure to carefully follow any washing instructions to help prevent the wool from felting.
If you have visible impressions or soft spots in a mattress then a topper normally won’t be an effective solution because it will just “follow” any soft spots or impressions underneath it. I would also check to make sure that the support system under your mattress is completely flat and doesn’t flex under the mattress because this can sometimes be the cause of any impressions in the sleeping surface as well. You can check this by putting your mattress on the floor to see if it makes any difference and if it does then it would “point to” your support system being part of the cause for any visible impressions or soft spots.
Some of the suggestions in post #4 here may be helpful as well if your mattress is too soft or there are visible impressions or soft spots in your mattress.
Thermal conductive materials or phase change materials can help to some degree with temperature when you first go to sleep at night but once the temperature equalizes the benefits don’t generally tend to last over the complete course of the night.
I don’t have any personal experience with Celliant but I have heard some good feedback about it from some people who have (and retailers that sell products with Celliant fabrics) and as you mentioned there is some science behind the claims. I certainly wouldn’t expect miracles and many people may not notice anything that they can specifically describe but you can read a little more about how it works here.
Having said that … I would be somewhat skeptical about any temperature regulation benefits from Celliant.
Phoenix