Ok - from what I have seen W&N has 2 types one is 100% cotton and the other is 80/20 however they both feel the same and everything I have seen on them and from my own experiences this is NOT preshrunk
For a table runner or topper I would use Thermore. I have used it a lot on table runners/toppers and even though it is polyester have never had an issue with something hot being placed on it causing a problem.
You will want to preshrink your fabrics also.