Preheat the oven to 450 degrees F (230 degrees C). Coat a 9- x 1-inch baking dish with cooking spray.
Combine potatoes, olive oil, garlic powder, onion powder, paprika, black pepper, and ½ teaspoon of salt in a large bowl; toss until evenly coated. Transfer to the prepared baking dish.
Bake in the preheated oven until potatoes are golden and fork-tender, 25 to 30 minutes. Set aside.
Meanwhile, cook bacon in a large skillet over medium, turning occasionally, until crisp, 10 to 15 minutes. Drain bacon on a paper towel-lined plate; remove and reserve 1 tablespoon drippings from the skillet. When bacon is cool enough to handle, finely chop, and set aside (about ½ cup).
In the same large bowl, combine chicken, cream cheese, water, scallions, hot sauce, ¼ cup of the bacon pieces, reserved bacon drippings, 1 ½ cups cheese, and remaining ½ teaspoon salt.
Fold chicken mixture into the potatoes in the casserole until well combined. Sprinkle with remaining ½ cup shredded cheese.
Bake until cheese is melted, 10 minutes longer.
Set an oven rack about 6 inches from the heat source and switch to the oven's broiler function. Broil on high for 3 minutes or until cheese is bubbling and brown in spots.
Garnish with remaining bacon (about ¼ cup) and additional scallions. Serve with sour cream.
