Prepare the slaw first: In a large bowl, combine both cabbages and cilantro. In a small bowl, whisk together mayo, lime juice, vinegar, honey, salt, and pepper. Pour the dressing over the cabbage and toss well. Refrigerate while you prepare the fish.
Season the fish: Pat the fish fillets dry with paper towels. In a small bowl, mix together chili powder, cumin, garlic powder, paprika, salt, and pepper. Drizzle fish with olive oil and lime juice, then rub the spice mixture all over both sides.
Preheat your grill: Heat your grill to medium-high heat (about 375-400°F). Clean and oil the grates to prevent sticking.
Grill the fish: Place fish on the grill and cook for 3-4 minutes per side, depending on thickness. The fish is done when it flakes easily with a fork and reaches an internal temperature of 145°F.
Warm the tortillas: While the fish cooks, warm your tortillas on the grill for about 30 seconds per side, or wrap them in foil and heat them on the cooler side of the grill.
Break up the fish: Remove fish from grill and let it rest for a minute. Use a fork to break it into bite-sized chunks.
Assemble your tacos: Place fish pieces in warm tortillas, top generously with cabbage slaw, and add your favorite toppings like avocado, extra cilantro, and a squeeze of lime.