I don't know if our expereine is relevant, because we use Langstroths, but we have both cedar and Swienty polystyrene. The external footprint of the poly is greater than that of the cedar because the walls are thicker, but internally they're exactly the same.

Crown boards (thick acrylic) and both framed and unframed queen excluders for the cedar hives can be used on the poly, leaving a rim of perhaps about half an inch of polystyrene uncovered which doesn't seem a problem. (The measurement is a guess, and I don't plan to brave the rain in the dark to check.) We haven't noticed any problems with rain getting in, maybe because the hive is strapped together.

The cedar roof won't fit the poly, it's too small but the poly roof could possibly be used with the cedar. There would be an overlap round the outside but the polystyrene slab of insulation beneath the metal outer lid would, I think, seal any gaps especially if ratchet straps are used.

The cedar brood box will sit on the poly floor, we haven't tried it the other way round, but think it would look ungainly.