I've been doing some research on plastic laminate flooring, and spotted a decision point regarding whether to use glue or not. Pergo recommends using glue even with their snap-together planks in areas where you'll have heavy furniture. The two-part glue is the glue itself and an activator, similar to an epoxy glue system, or auto body filler which uses a catalyst. The glue should not cause swelling along the seams since it is not water based. I could see a water-based glue such as white glue or carpenter's polyvinyl resin glue causing some swelling. Planks are only as good as the materials used to make them. A high density core is a factor, as is the quality of the wear layer on the surface.