Boil salted water and cook elbow pasta until just al dente according to package directions. Drain and set aside.
Melt butter in large saucepan over medium heat. Whisk in flour and cook 2 minutes, stirring constantly.
Slowly whisk in milk and half-and-half until smooth. Whisk frequently until mixture thickens and coats the back of a spoon, about 4-5 minutes.
Lower heat and stir in 3 cups cheddar cheese and paprika until melted and smooth.
Add cooked pasta to cheese sauce and stir to coat. Season with salt and pepper. Transfer to greased 9x13 baking dish.
Toss shredded chicken with BBQ sauce in a small bowl.
Preheat oven to 375F.
Sprinkle remaining 1 1/2 cups cheddar over mac and cheese. Distribute BBQ chicken evenly on top.
Bake 15 minutes until cheese is melted and top is golden brown.
Let cool 5 minutes. Drizzle with extra BBQ sauce and top with pickled red onions, jalapeƱos, and cilantro.