Hi xoration,
the Kapa-Plates are Cardboard, Foam, Cardboard which is much havier than Paper, Foam, Paper. There are many sources. I never used it.
The boards from Foamboarden.de are 15% heavier than the Boards from Modulor.de. The Boards from Modulor are 50% heavier than Dollar Tree foam.
Most of my planes are Modulor. Many parts of the FT Cruiser are Foamborden.
There is no big difference between both. Foamboarden is 5 cm longer, it's a bit harder. Modulor eats up more blades but bevel cuts are easier.