In a large bowl, whisk together mayonnaise, chipotle chiles, lime juice, olive oil, apple cider vinegar, and garlic. Season to taste with salt and pepper (I like 1/2 teaspoon salt and 1/4 teaspoon pepper).
Stir in cabbage, cilantro, and scallions. Cover and chill while preparing the fish.
To make the fish:
In a small bowl, combine chili powder, coriander, and cumin. Pat fish dry with paper towels and rub with 1 tablespoon olive oil.
Rub with spice mixture, then season to taste with salt and pepper. Place fish on a wire rack set over a rimmed baking sheet and refrigerate until grill is ready.
To use a charcoal grill:
Open bottom vent completely. Light large chimney starter filled with 6 quarts charcoal briquettes. When top coals are partially covered with ash, pour evenly over grill. Set cooking grate in place, cover, and open lid vent completely. Heat grill until hot, about 5 minutes.
Cleaning cooking grate, then brush generously with well-oiled paper towels until grate is black and glossy, about 5 to 10 times. Place fish on grill, perpendicular to bars of cooking grate.
Cook until the fish flakes apart when gently poked with a paring knife, about 10 to 14 minutes, gently flipping fish halfway through cooking time using 2 spatulas (fish should register 140 degrees on an internal thermometer). Transfer fish to platter, tent with foil, and let rest for 5 minutes while grilling tortillas.
To use a gas grill:
Turn all burners to high, cover, and heat grill until hot, about 15 minutes. Leave all burners on high.
Cleaning cooking grate, then brush generously with well-oiled paper towels until grate is black and glossy, about 5 to 10 times. Place fish on grill, perpendicular to bars of cooking grate.
Cook until the fish flakes apart when gently poked with a paring knife, about 10 to 14 minutes, gently flipping fish halfway through cooking time using 2 spatulas (fish should register 140 degrees on an internal thermometer). Transfer fish to platter, tent with foil, and let rest for 5 minutes while grilling tortillas.
To grill tortillas:
Working in batches, place several tortillas in a single layer on grill and cook until warm, about 10 seconds per side. Wrap tortillas in a clean dish towel or large sheet of foil.
To assemble tacos:
Cut each fillet into 3 equal pieces. To each warmed tortilla, add a piece of fish and top with cabbage slaw.