Basically a resophonic guitar is a mechanically amplified guitar. The string energy actually drives an aluminium speaker cone. In some ways they are a combination of a lap steel, and a speaker box, impersonating a guitar.

I've built a number of "square neck '' resophonic guitars, in the bluegrass music tradition ("Dobro" style). Some are flamed maple back, sides, & neck. Some are other woods, including Indian rosewood back, sides, & neck. All of them have been solid wood construction. (The vast majority of "Dobros" are plywood). I have a strong preference for using "John Quarterman" cones because of their superior tone and volume.