Hi drewy,
This would depend on the specifics of the microfiber and on the layers above and below the microfiber itself. There are many factors that combine together to regulate the temperature in a mattress (see post #2 here).
Microfiber can allow good airflow and can wick moisture but polyester fibers don’t absorb moisture into the fiber like natural fibers such as wool and cotton or even semi synthetic fibers such as viscose materials and in general natural fibers are better at regulating temperature than synthetic fibers. It would also depend on the thickness of the microfiber in the mattress pad and on how much it has compacted. Thicker layers of fiber that are less compacted over time will be softer than thinner or more compacted layers. If your microfiber mattress pad has a waterproof layer such as a polyester semi breathable membrane then this would restrict airflow through the material and would also have a warming effect on temperature for some people as well (see post #89 here about mattress protectors).
The Natura washable wool mattress pad doesn’t have a lot of wool in it so it wouldn’t be especially soft in terms of adding to pressure relief or padding pressure points but it also doesn’t have a waterproof membrane which would restrict airflow and wool is a better temperature regulator than polyester so it would probably help with temperature regulation more than your current mattress pad.
Thicker wool mattress pads or toppers would be softer and would probably regulate temperature better than a thinner mattress pad but wool in general won’t be as soft as a soft foam material and compressed wool can reduce the contouring effect of any foam layers underneath it. You can read more about wool mattress pads in post #10 here and wool toppers in post #3 here.
In general if you need a significantly softer sleeping surface I would consider adding a softer more pressure relieving foam material on top of your mattress and then using a wool mattress protector or mattress pad (not waterproof) for temperature regulation or alternatively using a thicker wool topper (which won’t likely feel as soft as foam but can help to pad some of the pressure points).
Phoenix