Preheat the oven to 375 degrees. Line a cookie sheet with parchment paper or foil.
Scrub and Rinse the potatoes. Place them in a large pot and cover them in water and about a tablespoon of salt.
Cover and bring to a boil. Reduce the heat to medium-low and simmer for about 10-15 minutes or until the potatoes are fork tender. The amount of time it takes to boil your potatoes will vary depending on the size of the potatoes.
Once tender, remove the potatoes from the water and allow them to cool.
While the potatoes cool, add the bacon to a baking sheet lined with parchment paper or foil and bake for about 15 minutes or until it's crispy. Remove the bacon from the oven, turn the heat down to 350 degrees and crumble bacon into small pieces and allow it to cool on a paper towel to remove excess bacon grease.
Add the mayonnaise, sour cream, green onion, smoked paprika, garlic powder, 1/2 teaspoon salt, black pepper, milk, 4 ounces of shredded cheddar, and the bacon crumbles (reserve about 2 tablespoons of crumbled bacon for the topping) to a large bowl and stir to combine.
Chop the potatoes into 1/2-inch pieces or thin slices. Add the potatoes to the sauce and stir to combine.
Pour the potato/sauce mixture into a 9x13 casserole dish. Sprinkle the top with the remaining 4 ounces of shredder cheddar and bake at 350 degrees for about 25-30 minutes or until the potato salad is warm and the cheese on top is thoroughly melted.
Top with the remaining 2 tablespoons of bacon crumbles. Sprinkle about a tablespoon of finely chopped pieces of the green portion of the green onions on top (optional).