Preheat waffle iron to medium-high heat. Lightly coat grids with cooking spray or oil.
Separate eggs, placing yolks in a large bowl and whites in a clean, dry medium bowl.
In a separate medium bowl, whisk together white whole wheat flour, baking powder, baking soda, salt, and cinnamon.
To the bowl with egg yolks, add buttermilk, Greek yogurt, maple syrup, cooled coconut oil, and vanilla. Whisk until smooth and well combined.
Pour dry ingredients into wet and stir gently with a spatula just until combined. Small lumps are fine; don't overmix.
Beat egg whites with an electric mixer on medium-high until stiff peaks form, about 2-3 minutes.
Fold one-third of the egg whites into batter to loosen, then gently fold in remaining whites until white streaks disappear.
Pour about 3/4 cup (180ml) batter onto preheated waffle iron and cook 4-5 minutes until steam significantly reduces and waffle is golden and crisp.
Carefully remove waffle to a wire cooling rack in a single layer. Repeat with remaining batter, re-oiling iron before each waffle.