Yes, Heather. All your guesswork are right. Gouache more opaque then watercolor.This paint draw almost as acrylic or oil by layers, but gouache is well diluted with water like watercolors. I usually bring in jars of many different shades and draw them. Not so long ago I had a picture on instagram, where many,many of these jars of gouache.
RE: Real mystery of gouache artworking