Hi TheSleeplessCat,
Perhaps the best “first” suggestion would be to give your new mattress a little time. When you buy a new mattress it can sometimes take a few weeks for the mattress to 'break in" and for your body to adjust to a new sleeping surface … especially if it is significantly different from your old mattress. We can develop a “sleeping memory” (like a certain posture that has become a “habit”) and it can take some time for muscles and ligaments to loosen and relax so that a new mattress is comfortable … even if it provides better alignment than your old one. It’s somewhat like a new pair of shoes that can take some time before it becomes as comfortable as they will be in the long term. If for example you buy a new pair of shoes has better arch support than your old pair … it may not be comfortable at first even though after a while it’s can be hard to imagine how you wore anything else.
If it turns out that you do need an extra topper … then what type of topper is “best” for you would depend on your own personal preferences and also on the specific “symptoms” you were trying to correct. A mattress that contributed to back pain in some part of your spine may need a different type of topper than a mattress that caused you to feel pressure points in a certain area. If you are only looking for a different (or softer) “feel” but there are no specific symptoms … then this too could result in a different choice.
Out of the options you listed … memory foam is a slow response material which will give you a more “in the mattress” feeling. Polyfoam and latex will be a more lively and resilient surface which will be more of an “on the mattress” feeling. The “pillowtop” feeling would generally be similar to a low ILD polyfoam or latex but using a foam topper that is too thick or soft can compromise alignment and create a different problem. Wool can also be a great choice because it can provide some cushioning for pressure points and added ventilation and temperature control without compromising alignment. Other synthetic fibers (like polyester) would be similar but without the extra benefits or durability that comes from the use of natural fibers like wool. Featherbeds and/or down can add some surface softness but are higher maintenance (require fluffing up) and are generally not the best performing material in a topper.
So the first step is time … and then if you need a topper I would try to identify exactly what you are trying to change (pressure relief, feel, support, etc) and a more specific description of where you are feeling any “symptoms” that you are feeling to help you decide which type of topper may work best for you. Post #10 here may also be helpful in deciding on what you need.
Phoenix