Bias is also often used to create stems for appliqued flowers. Bias strips can be stretched to go around curves. The edges can be hand or machine sewn to the background fabric. Hand quilters often used to quilt right over appliques. Nowadays it's more common to quilt around appliques.
The gridded fusible is used for a very specific type of wallhanging construction. It makes the fabric too stiff for bed quilt use. It's not a technique I would recommend to a beginner. Better (IMO, anyway) to learn basic techniques first.