Just wondering...What type of circuit boards does McIntosh use.... in lets say..the MC352 and C42 ?

What do you mean? Most parts are through-hole instead of surface mount if that is what you want to know. In fact it seams that they only do surface mount when though-hole part are not available. I wonder if there is a sound, reliability or simply manufacturing reason behind this.

I don't know if they use more than two layers, didn't look that close to the circuit.

Look like G10 fiber glass boards to me.

I heard of different kinds like,
double sided,
epoxy,
farraday
...just wondering

Mac used fiberglass in the 1960's, my MA230's preamp board is fiberglass and is assembled very well.