As bjchad said, do sew down every element that was fused on to your quilt...fusing isn't forever and it will come loose (ask me how I know!). I would quilt around all the fused areas, then using painter's tape as a guideline, do a diagonal cross-hatch grid 1" apart to keep everything from sagging, but don't do the cross-hatch over the applique. How far apart you quilt is determined by the batting you use...some need to be quilted 4" apart and some are good with 10". If I can lay my hand down on a quilt and not touch quilting, I don't think it is quilted close enough together. It is beautiful and I can't wait to see what you do with the quilting.