Preheat the oven to 350 degrees F (175 degrees C). Grease a 1 1/2-quart baking dish.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Drain and return to pot; set aside.
Melt butter in a saucepan over medium heat. Add onion and jalapenos; cook until just softened, 3 to 5 minutes. Add garlic and cook until fragrant, 1 to 2 minutes. Mix in flour, coating vegetables well. Whisk in milk slowly until smooth. Bring to a simmer, whisking constantly until thickened, about 3 minutes. Reduce heat to low.
Season sauce with garlic powder, seasoned salt, black pepper, and Worcestershire sauce. Stir in processed cheese and cream cheese until melted and sauce is smooth, about 5 minutes. Season with salt.
Pour macaroni into cheese sauce and stir to coat completely. Pour into the prepared baking dish.
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain bacon slices on paper towels. Cool briefly.
Crumble bacon and mix with panko bread crumbs and Parmesan cheese in a small bowl. Sprinkle evenly over macaroni. Top with jalapeno slices.
Bake, uncovered, until browned and bubbly, 30 to 40 minutes. Let cool for 10 minutes before serving.
