Pat the fish fillets dry with paper towels. In a small bowl, mix the chili powder, cumin, smoked paprika, garlic powder, salt, and black pepper. Rub this spice blend evenly over the fish, then drizzle with lime juice for added flavor.
Heat olive oil in a large skillet over medium-high heat. When the oil is hot, add the seasoned fish fillets and cook for 3 to 4 minutes on each side, depending on thickness, until the fish is golden brown and flakes easily with a fork. Remove the fish from the skillet and break into large chunks.
In a large bowl, combine the green cabbage, purple cabbage, and chopped cilantro. In a smaller bowl, whisk together mayonnaise or Greek yogurt, lime juice, honey, salt, and black pepper. Pour the dressing over the cabbage mixture and toss thoroughly to coat.
Heat a dry skillet over medium heat. Warm each corn tortilla for about 30 seconds per side until soft and slightly charred. Keep tortillas warm by wrapping them in a clean kitchen towel.
On each tortilla, place a few chunks of cooked fish. Top with a generous amount of cilantro lime slaw, then add sliced avocado and sprinkle with crumbled queso fresco or feta cheese if using. Serve with lime wedges on the side for an extra burst of freshness.