I can't really say that I've seen that much difference between a hopping foot and a gliding foot, though I haven't used a Janome. Loops on the bottom could be from a variety of causes. The first thing I'd try is put on a regular or zigzag foot and try sewing a line on a scrap of fabric. If it's still making loops, that would rule out your quilting foot as a source of difficulty. Maybe the bobbin thread missed the tension? Sometimes my machines will do that sort of thing only because there is lint under the bobbin case. Recently I had similar problems that turned out to be caused by a rough spot on the edge of a plastic bobbin. The thread would catch on it and then pull loose, and of course that varying stress broke the upper thread several times before I figured out the cause.