I love the 2" foam. It’s very strong, which was a bit of a surprise to me. In one famous incident, the guy who’s been helping me build the railroad actually was lying on top of the foam. Since he is a very large man, I was impressed that the foam had no trouble holding him up. I took a picture of it, but I can’t find it (besides, he would kill me if I posted it). Anyhow, the point is that the 2" foam is strong, and easy to mold for scenery, mountains, etc.
I have used plywood with homasote and 2" foam on my layout all with Midwest cork roadbed. I found the foam to be quite noisey.