Raven Eagle

The second triggered ability can trigger only once each turn. It doesn't matter whether Raven Eagle was on the battlefield when the first card was drawn. If it's not on the battlefield when the second card is drawn, the ability can't trigger at all that turn. It won't trigger when the third or fourth card is drawn.

Creating a Clue token this way isn't the same thing as investigating. Notably, an ability that triggers whenever you investigate won't trigger because of creating a Clue token this way.

Clue tokens are artifact tokens with "{2}, Sacrifice this token: Draw a card."

If a card or ability instructs you to put cards into your hand without specifically using the word "draw," it's not a card drawn.

If an effect instructs you to draw multiple cards, the ability triggers after you draw whichever is the second one for the turn. It goes on the stack after you've drawn and looked at all the cards and finished resolving the spell or ability that caused you to draw them.