Certainly! You will receive the Stretch Goals applicable for the game(s) you pledged. For instance, if you only back Raiatea, you will get the 10 Additional Rituals for Raiatea, but no Stretch Goals for Counterfeiters or Firenze. The same holds for backing just Counterfeiters or Firenze. If you back the bundle consisting of those three games, you will receive all Stretch Goals, including The Game Changers.