What kind of yogurt do you use in this recipe...Greek yogurt ok?

sorry: vary, not very; as L-J recommends.

Greek yogurt has had whey drained off. It will very in thickness according to how much it has been drained -- thus adjusting as Lindsay-Jean is needed to bring it back to the looser consistency of intact/as originally made from milk yogurt, with all its whey included. The thickness of the soup is in your hands!

Yes, it would be fine to use Greek yogurt! And if the soup is slightly thicker as a result, you could always add a touch more water if desired to thin it back out.