R12 is a better refrigerant, but it hurts the ozone layer & it's now illegal to manufacture it. Still can be bought & used (with a license), but nobody's supposed to be making any more of it.

A '97 almost certainly came with R134a, so there's no conversion needed. Everybody switched over in the early '90s.

The mist coming out of your vents was probably water vapor. It was probably on a very humid day, right?