The above are examples of atypical construction.
I believe Clayton are pre-fab homes with metal studs.
The other issue of HORIZONTAL studs might be explained by home-owner modification dividing a space to create two spaces, and the wall was never intended to bear weight (no permit pulled, thus, no standard method used!)
I would re-consider a wall mount trial. Instead, consider buying a floor stand or table mount. Last, resort is to open the drywall and build a box frame interior to the wall on which you will hang the mount.
For those of us with standard construction, but off center studs as I have, I like the idea of applying a plywood facing or 2X10 across the vertical studs exterior to the drywall. For my safety I will consider two sheets of 3/4 plywood for 112# plasma on omnimout because it cantilevers about 26" away from the wall. Its just not a finished, quality look.
I worked construction and do not fear a re-model, know the materials and tools needed. Don't start a project you can't finish!