For chicken: Whisk first 6 ingredients in deep medium bowl to blend. Place milk in second bowl, eggs in third bowl, and ground cornflakes in fourth bowl. Working with 4 chicken strips at a time, place in flour mixture and toss to coat. Dip same chicken strips into milk, then eggs, then cornflake crumbs, coating with each; arrange on sheet of foil.
Pour oil into heavy medium saucepan to depth of 2 inches. Attach deep-fry thermometer to side of pan; heat oil to 335°F to 350°F. Working in batches, add coated chicken strips to hot oil and fry until golden and cooked through, turning occasionally, about 3 minutes. Using slotted spoon, transfer chicken strips to paper towels to drain. Cut strips into 1-inch-long pieces.
For macaroni: Cook macaroni in large pot of boiling salted water until just tender but still firm to bite. Drain; transfer to very large bowl. Mix in green onions and oregano.
Melt 6 tablespoons butter in same large pot over medium heat. Add 3 cups chopped onions and garlic. Cover; sauté until onions are soft but not brown, stirring often, about 6 minutes. Add flour; stir 2 minutes. Gradually whisk in milk. Bring to boil, whisking constantly. Reduce heat and simmer sauce 2 minutes. Add all cheeses, paprika, 1 teaspoon salt, and 1 teaspoon pepper. Whisk until cheeses melt and sauce is smooth, about 2 minutes. Remove from heat. Season to taste with more salt and pepper, if desired. Mix cheese sauce into macaroni. Mix in chicken pieces. Mound mixture in 13x9x2-inch glass baking dish. DO AHEAD Can be prepared 2 hours ahead. Let stand at room temperature.
Preheat oven to 350°F. Stir hot pepper sauce and remaining 2 tablespoons butter in small saucepan over medium heat until butter melts; spoon 4 tablespoons over macaroni in dish. Bake macaroni uncovered until heated through, about 30 minutes, or 45 minutes if made ahead. Serve, passing remaining butter and hot-sauce mixture separately.