OBW is made from a single fabric (except for borders, and hollow cubes that may be added). Stack and Whack and FPP almost always feature sashing made from different fabrics than the one used for the patches.
OBW can be 6 or 8 layers. The design was first published by Maxine Rosenthal. Stack and Whack is the brain child of Bethany Reynolds, and can be various numbers of fabric layers - as far as I know. FPP is the name used by Mary Lou Hallenbeck of HD Designs for a 4-layer design. I think that kaleidoscope usually refers more to a "look" (pattern repeating around a central point) than to a specific design, although Ricky Tims does have a Kool Kaleidoscope design available, and it's nothing like the others mentioned, but lots of fun to make.