Well ... to some extent you've pretty much answered your own question already : you get the output from Wrap, then attach it to whatever body you need it to be attached to (either by actually welding verts, or by just manipulating normals at the edges to make things visually seamless). Wrap3 doesn't "autoretopo" anything…
I want to try using the Wrap3d / Texture XYZ workflow on a head sculpt, where it auto retopos your sculpt to one of their meshes so you can use all the texture maps but I'm not sure how I would put the head back onto the body whilst keep all the maps and same topology
The more "typical" workflow for these type of assets would be to wrap the asset to your mesh and transfer/bake the maps (without the need to mess with your geometry). Asset vendor should also have tutorials/documentation to show you how to do it (i.e. tex xyz has videos for their Vface assets).