1. Preheat oven to 375°.
2. To prepare shortcakes, line a baking sheet with parchment paper, and set aside.
3. Weigh or lightly spoon baking mix into a dry measuring cup; level with a knife. Combine baking mix, 2 tablespoons sugar, and cinnamon in a medium bowl, stirring with a whisk. Make a well in center of mixture. Place egg whites in a small bowl; stir with a whisk. Add buttermilk, 1 teaspoon orange rind, and 1/2 teaspoon vanilla, stirring with a whisk. Add to baking mix mixture, stirring just until moist. Spoon batter into 4 mounds 2 inches apart on prepared baking sheet.
4. Bake at 375° for 13 minutes or until golden.
5. To prepare topping, while shortcakes bake, combine 1/2 teaspoon orange rind and next 3 ingredients in a medium bowl. Add mango and berries, stirring gently to coat.
6. Cut shortcakes in half horizontally using a serrated knife. Place 1 shortcake bottom in each of 4 shallow bowls. Spoon about 1/2 cup mango mixture and 1/4 cup yogurt, if desired, over each shortcake bottom. Top with shortcake tops.