I’d skip the chipboard and all its cousins (particle board, etc). I use plwood and pine boards both depending on usage. While I understand the advantages of cdx, I prefer bc it’s easier on the hands and if the layout gets so wet the plys separate, you probably have to rebuild anyway. I also use screws instead of nails and am a recent convert to squarehead. Trim sheetrock screws have the squarehead, but I prefer stainless steel with a larger shank.
Enjoy
Paul
This depend upon what type of plywood you are buying too. If you are buying A/C plywood with a knot-free finished side, this is true. But when you are covering the plywood with scenery, why do you need such a finish? I use B/C plywood which has a few tight knots on the B side and is not sanded quite as finely as A/C, but has a perfectly workable surface for railroading. I have used CDX as well which is rougher on the C side but still workable. The wafer board is more expensive in comparable thicknesses than either B/C or CDX–one more reason to skip it and go with the plywood.
Ron