This is a quick overview of all non-exposed registry keys VP parses.
(some might not work correctly anymore, who knows)

"Player" / "Stereo3D"         non-exposed/beta feature: setting this to 2 enables scanline interleaved mode (the LGs i have use that for example)
"Player" / "PhysicsMaxLoops"
"Player" / "GlobalDifficulty" chooses slope/scatter/flipper difficulty of all tables (0..100, easy..difficult)
"Player" / "Autostart"        presses start after loading a table automatically
"Player" / "AutostartRetry"
"Player" / "asenable"         enable autostart? (0 or 1)
"Player" / "mirror"           mirror playfield (also mirrors keys accordingly) (0 or 1)
"Player" / "Exitconfirm"      seconds that escape key has to be pressed to exit VP completely
"Player" / "Volmod"           sets default sound mixer volume (0..1000)