My cupcake recipe calls for a 1/2 cup sour cream. Does substituting the sour cream for plain yogurt change the flavor or consistency?
Go right ahead. The flavor will be a bit different, and the batter somewhat thinner, but it's a lovely idea. Do it!
I agree that it should be no problem, but if possible, use a full-fat Greek yogurt for the best flavor. In fact, I use Greek yogurt all the time in place of sour cream. It has more protein and less fat.