It does not target the cards, but it targets the opponent. If you can’t target an opponent, you can’t activate this ability.
, : Reveal the top three cards of your library. Target opponent chooses one of those cards. Put that card into your graveyard, then draw two cards.
After the opponent chooses which card to put into your graveyard, you draw two cards regardless of how many were actually revealed or how many you have left in your library.
, 
: Reveal the top three cards of your library. Target opponent chooses one of those cards. Put that card into your graveyard, then draw two cards.