I'm used to working with the sheets of pink or blue insulation foam; the bead-style of Styrofoam in your pics are good for making bases for other things to sit upon. The bead-style Styrofoam, (in my experience, for my builds) has been too prone to shedding parts of itself, or unexpectedly breaking or loosing dimensional integrity. Sure, we are all makers here and and can create anything with stuff that we possess instead of the stuff we really need.... but. That bead-style of Styrofoam is a bear to usefully model with.
I'm trying to not be the one with all the negative waves and all - definitely best of luck!