I think the big difference between the Sharon Schamber product and the Wash-Away product is that the latter has one side that is fusible.
I have used freezer paper for years for machine applique, a la the Harriet Hargrave method of turning under the edges. For me, it is much easier to use paste (that comes in a small tub) to turn under the edges than a glue stick. Anyway, I did try Sharon Schamber's product for this same method but found that the edge was too soft for me. Freezer paper is a little more stiff.