I don't know the effect of propylene glycol (PG) and glycerin on the pH. They appear to increase the tongue bite by lowering the combustion temperature of the tobacco, and producing clouds of vapor particles. (PG seems to be the secret to the dense clouds yielded by vape ignition.)
I have placed a tray of unflavored, commercial "black Cavendish" into a toaster oven, and gently heated it, in an attempt to dry it. The result was a tenacious coating of viscous PG on the interior of the oven. What does this do to your tongue? I don't know.
Bob