Place cubed potatoes in a large pot, cover with cold water, add 1 teaspoon salt, and bring to a boil. Reduce heat and simmer 12–15 minutes until potatoes are fork-tender but still hold their shape.

Meanwhile, add chopped bacon to a cold large skillet. Cook over medium heat, stirring occasionally, 8–10 minutes until bacon is golden and crispy. Transfer bacon to a paper-towel-lined plate; reserve bacon fat in the skillet.

Add diced onion to the reserved bacon fat and sauté over medium heat for 5 minutes until softened and lightly caramelized. Stir in minced garlic and cook 30 seconds. Remove from heat.

In a medium saucepan, melt butter over medium heat. Whisk in flour and cook 2 minutes, stirring constantly, to form a light golden roux.

Gradually whisk milk into the roux. Cook, whisking, 5–7 minutes until the sauce thickens enough to coat the back of a spoon. Remove saucepan from heat; stir in 2 cups shredded cheddar, sour cream, smoked paprika, black pepper, garlic powder, cayenne, and salt to taste until smooth.

Drain potatoes thoroughly and transfer to a large mixing bowl. Add sautéed onion-garlic mixture, three-quarters of the crispy bacon, and the swamp sauce. Gently fold to coat potatoes without breaking them up.

Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish and spread the potato mixture evenly inside.

Sprinkle remaining 1 cup shredded cheddar and reserved bacon over the top.

Bake uncovered for 25–30 minutes until the cheese is melted, the edges are bubbling, and an internal temperature of 165°F (74°C) is reached. For an extra-crispy top, broil the last 2–3 minutes, watching closely.

Remove from oven and let rest 5 minutes. Garnish with sliced green onions just before serving.