Preheat the oven to 425 degrees F. Mix the grits and 1 1/2 cups water in a large microwave-safe bowl and microwave until thickened, about 4 minutes. Stir occasionally until slightly cooled. Meanwhile, coat four 10-ounce ramekins with cooking spray and sprinkle with parmesan; tap out the excess. Place the ramekins on a baking sheet.
Combine the cooled grits, corn, cream cheese, egg yolks, thyme, 1/2 cup parmesan and 1/4 teaspoon each salt and pepper in a blender. Puree until smooth, stopping the motor to stir by hand if needed (the mixture will be thick). Transfer to a large bowl.
In a separate bowl, beat the egg whites and 1/2 teaspoon vinegar until medium peaks form. Fold one-quarter of the whites into the grits mixture, then fold in the rest. Pour the batter into the prepared ramekins. Bake until puffed and golden, 20 to 25 minutes. Toss the arugula with the remaining 1 tablespoon vinegar, the olive oil, and salt and pepper to taste. Serve with the souffles.