Wash and peel the potatoes. Cut them into thin fry shapes, about ¼ inch thick.
Soak the potato fries in cold water for 30 minutes to remove excess starch. Drain and pat them dry with paper towels.
In a large pot or deep fryer, heat vegetable oil over medium-high heat to 350°F (175°C).
In a mixing bowl, combine chili powder, garlic powder, onion powder, paprika, salt, and cayenne pepper. Toss the dried potato fries in the spice mixture until evenly coated.
Carefully add the fries to the hot oil in batches, frying until golden brown and crispy, about 4-5 minutes per batch. Use tongs to remove them and place on a baking sheet lined with paper towels to drain excess oil.
In a small saucepan over low heat, combine shredded cheddar cheese, milk, and taco seasoning. Stir until the cheese melts and the sauce is smooth.
Serve the fries hot with the cheese sauce, sour cream, and salsa on the side for dipping.