When batting fibers migrate through the fabric it is called bearding. It used to be a big problem with poly batting but manufacturers heard us and now resin coat their poly battings which prevents bearding. Two I have had very good luck with are Hobbs Polydown and Quilters Dream poly.
Scrim is a very sheer polyester "foundation" for lack of a better word that cotton battings are needle punched to. The reason for scrim is to give the cotton batting more strength and stability and to allow greater distance between quilting stitches. The 100% cotton batting without scrim needs to be handled very gently or it will tear apart quite easily and it must be quilted a minimum of 2" while cotton battings with scrim can be quilted up to 10" apart and can be manhandled quite a bit without tearing.
With W&N batting there is a right side and wrong side. If you hand quilt it makes little difference but machine quilting or LA quilting the bumpy side should be against your quilt top. I always remember it by "bump is up". Here is a great blog about it with close up pictures
http://pamhollanddesigns.typepad.com...o-batting.html