In a large bowl, whisk mayonnaise, sour cream, 1 tablespoon lime juice, honey, 0.25 teaspoon salt, and 0.25 teaspoon black pepper. Add green cabbage, red cabbage, carrots, and cilantro; toss to coat. Refrigerate while you cook the fish.
Pat fish dry. In a small bowl, combine chili powder, cumin, smoked paprika, garlic powder, 0.5 teaspoon salt, and 0.25 teaspoon black pepper. Sprinkle evenly over the fish, then drizzle with olive oil and 1 tablespoon lime juice.
Heat a large skillet over medium-high. Add the seasoned fish and cook 2 to 3 minutes per side, until opaque and it flakes easily with a fork. Transfer to a plate and rest 2 minutes, then gently flake into large pieces.
Warm tortillas in a dry skillet 30 to 60 seconds per side (or wrap in a damp towel and microwave until pliable).
Assemble tacos: add a scoop of slaw to each tortilla, top with warm fish, avocado slices, cotija, and pico de gallo. Finish with a squeeze of lime.
Serve immediately with extra cilantro and lime wedges on the side.
Notes
Swap cod with salmon or shrimp. For a lighter slaw, use Greek yogurt in place of sour cream. Warm tortillas directly over a gas flame for light char. Leftover slaw keeps 1 day refrigerated; assemble tacos just before serving to keep them crisp.