Hi Brick,
The choice of mattress protector is really a matter of preference and which of the different types offers the performance and qualities that are most important to you. Post #89 here has a description of some of the different types and the tradeoffs between their effect on the mattress, their effect on sleeping temperature,and the degree or water resistance that are involved. If sleeping temperature is the biggest issue … then a more breathable topper may be beter than the thinner types that have a “semi breathable” membrane that in some cases can raise sleeping temperature (see post #2 here for all the different factors that can affect sleeping temperature).
If you are choosing something thicker than a mattress protector (such as a mattress pad or topper) then personal preference as well as the specific type of “fine tuning” you are looking for would be the way to decide between them.
The choice of blankets and bedding that is over you is strictly a matter of temperature regulation and the type and thickness of material you are most comfortable with. Because they are over the body … they won’t affect the “feel” of the mattress (except to a degree with memory foam which is temperature sensitive) and would be more of a matter of how warm or cold you want to be, humidity control, the room conditions, your comfort level with natural vs synthetic materials, the weight of the blankets (some like heavier and some like lighter) and other personal preferences.
A mattress pad or a topper is more about fine tuning the feel and performance of a mattress and would really only be necessary if you wanted to fine tune the mattress in some way or wanted to change the “surface feel” of the mattress. Post #10 here talks about some of the options for mattress pads.
I would tend to use a thinner protector rather than a thicker mattress pad or topper unless you were clear that you wanted to fine tune the mattress in a specific way. I wouldn’t introduce a second variable until you have made all your final choices with your mattress.
Phoenix