xNormal? Then I would bake with an external cage file (inflated, smooth-shaded lowpoly). I thought the screenshot showing the projection errors was from Painter.
more of a problem, with the the lowpoly than the high, though you will get a better edges, if you model it in, or float it. and even in the lowpoly you can get by complications with projection by simpley explodeing the mesh, and bakeing that way.
it sounds like you're not excluding the lowpoly mesh from the ao bake in the material shader, if you set exclude to -1 and then in the object property's of the lowpoly mesh set object ID to 1 it should work
I learned that when you are dealing with baked normals you cant delete the other side because that would change the normals of the lowpoly and then you will no longer have synced normals between the lowpoly and the normalmap.
uh, I guess some would call it lowpoly art - flatcolored-ish? I wouldn't say its trying to be low poly but its has some similar looks to other lowpoly works :)