That hypothetical 92 degree ideal setting is not even that. As the Wallytools people point out, one has to set the 92 degrees when the stylus is actually dragging when the record is in motion. They utilize a special microscope and take measurements with the surface in motion.
I prefer setting VTA by ear after first getting the body of the cartridge close to parallel to the record surface. I too utilize a typical thickness record and don't bother to make changes for different thickness records.
There is one extremely rare version of the linear tracking Air Tangent arm that provided for VTA adjustment on the fly using remote control--that would be the ideal way to set VTA for each record (there is a numerical readout, so one could record the number for each record once that is done by ear). I am actually glad I don't have this kind of capability because I really don't want to bother with that kind of fiddling around.