I do a machine blanket stitch around appliqués done with wonderunder. I feel the wonderunder does help to prevent some of the edges from fraying but they do still fray from repeated washing. I have not had any appliqués come off from fraying.
If you want to use an Elmer’s glue stick to temporarily hold down an appliqué, I would recommend machine sewing a straight stitch inside the appliqué edge at about 1/8 inch. The edges past the 1/8 would fray but the straight stitching should hold the appliqué on with repeated washings.