Cut & season. Slice potatoes into ½-inch sticks; soak 30 min for extra crunch if time permits. Pat dry and toss with olive oil, garlic powder, onion powder, smoked paprika, salt and pepper.
Bake. Arrange in a single layer on a lined sheet; roast at 425 °F (220 °C) for 25–30 min, flipping halfway, until deeply golden.
Prep toppings. While fries bake, sauté diced onion and bell peppers 3–4 min in a drizzle of oil until slightly softened. Shred cheeses.
Mix sauce. Whisk sour cream, mayonnaise, lemon juice, garlic powder and smoked paprika until smooth; set aside.
Load & melt. Transfer hot fries to an oven-safe dish, blanket with cheddar and mozzarella; return to oven 3–5 min until cheese bubbles.
Finish. Scatter sautéed veg, jalapeños, chili flakes and oregano over melted cheese, drizzle with smoky sauce, garnish with parsley. Serve piping hot.