Place tofu on several layers of paper towels; cover with additional paper towels. Let stand 30 minutes, pressing down occasionally. Cut tofu into 1/2-inch cubes, and toss with cornstarch.
Prepare noodles according to package directions, omitting salt and fat. Drain well; set aside.
Combine ketchup, sugar, fish sauce, and Sriracha. Heat 1 tablespoon oil in a nonstick skillet over medium-high heat. Add tofu to pan; sauté 7 minutes or until golden. Remove tofu from pan.
Heat 1 teaspoon oil in pan. Add eggs and egg white; cook 30 seconds, stirring constantly. Remove from pan. Heat remaining 2 teaspoons oil in pan. Add noodles; cook 3 minutes. Stir in ketchup mixture; cook 30 seconds. Add egg mixture; cook 1 minute, stirring often. Remove from heat; stir in onions and cilantro. Place 1 cup noodle mixture on each of 4 plates. Top each with 1/2 cup tofu and 1 1/2 teaspoons peanuts. Serve with lime wedges.