I have always used Hobbs 80/20 for over two decades. Back in the old days, Warm & Natural actually had tiny pieces of wood embedded in it. I find that W&M is denser and heavier in weight. Hobbs gives a slight puff to the quilt.
Sandwiches are a good ideal. Before quilting, I always use one to make everything is correct. Keep your quilting simple and gradually work into the more difficult designs. Harriet Hargrave has a really good book called Heirloom Machine Quilting. Good Luck !!