I use tear away a lot. If the design is dense I tear away from the edges and the rest remains covered by the design. I have also used Ricky Tims stable stuff, which is a cut away. What stays under the design, when wet, becomes a veryt thin layer of poly that will not change the loft of the batting. If making, for example, a towel, I use wash away under and over the terry cloth to help the threads on the towel lay down and not bounce back to to cover the embroidery design. If you are quilting all the back will be covered never to be seen again.
When embroidering a garment, I tend to use tear away rather than stable stuff and iron fabric with fusible on the back because the back of the embroidery can be scratchy on the skin.