Can I use Frigid Touch on 2 different units?

No, you cannot use Frigid Touch on two different units with a single casting.

According to the card text, Frigid Touch says: "Give a unit -2 [S] this turn." Because it specifies a single target, you must choose one unit when you play the spell.

If you choose to pay the [Repeat] cost, you perform the entire instruction again. For the repeated instance, you may choose the same unit again or a different unit, as the "repeat" allows you to resolve the spell's effect a second time.