Make the chipotle crema: In a small bowl, whisk the mayonnaise and sour cream until combined. Squeeze in lime juice, to taste, and whisk. Add salt, pepper and chipotle, to taste.
Make the tacos: Heat a large skillet over medium heat for 3 minutes. Meanwhile, pour a few tablespoons of oil in a small bowl. Separate the corn tortillas from each other but keep them in a stack then run the outer edges through the oil. Add a few tortillas at a time to the dry skillet and heat until soft and hot, about 30 seconds per side. Wrap the tortillas in a clean, dry kitchen towel or place in a tortilla warmer, to keep warm.
Heat a grill pan or grill over high heat for at least 5 minutes.
Meanwhile, slice the fish fillets into 1-by-2-inch strips. Pat dry with a paper towel. Season generously with salt and a pinch of pepper.
Wipe the grill pan or grill grates with a lightly oiled towel right before cooking to remove any char and debris. (This will give you great grill marks and help the fish from sticking.) Working in batches, cook the fish strips in a single layer just until they are opaque and flake in the middle (making sure not to overcook them), about 2 minutes per side.
Top each tortilla with 3 fish strips, a pinch of the cabbage and a drizzle of the crema. Serve right away with lime wedges and pico de gallo or hot sauce on the side.