I love Steam A Seam 2. Never had any trouble with it. I
do blanket stitch or satin stitch around all of the edges, though.
As far as embellishments, I would prefer that they be included separately ... NOT sewn on yet. I have a mid-arm quilting machine. It would be super-easy to overlook a button (etc.), and stitch right over it, potentially damaging the machine.
IMO, the best thing is to ask the block owner about applique' or embellishments, and whether to sew the embellishments on or include them separately.