In a small bowl stir the cayenne and paprika together. Cut the white fish fillets into about 4 strips per fillet and season with cayenne/ paprika mixture, salt and pepper.
Heat a large non-stick sauté pan over medium heat, add the vegetable oil and heat through. Add the strips to the pan, working in batches if necessary so the pan is not overcrowded.
Cook the fish until it easily lifts from the pan, about 3 minutes. Flip the fish and cook until just cooked through, about an additional 3 minutes. Set aside and cover.
For the cilantro white sauce:
Mix the sour cream, mayonnaise, garlic, lime juice, cilantro and black pepper together in a small bowl.
Cover and refrigerate for at least 15 minutes.
For serving:
Toss together the shredded cabbage to combine.
Add some of the shredded cabbage to warmed tacos and top each with a slice of fish. Top with pico and about a tablespoon of the cilantro lime sauce. Serve with lime wedges.