If you exile a double-faced creature card this way, you'll pay the mana cost of the front face. The token will be a copy of the front face and it won't be able to transform.

Although you're paying the card's mana cost, you aren't casting that card. Abilities that reduce the cost to cast a creature spell won't apply, and additional costs to cast that creature can't be paid. Alternative costs that affect what it costs to cast a creature spell, such as evoke, can't.

Any "enters" abilities of the creature will trigger when the token enters. Any "as [this creature] enters" or "[this creature] enters with" abilities of the creature will also work.

If the exiled creature card has {X} in its mana cost, X is considered to be zero.