In a small vessel, combine chili powder, cumin, garlic powder, and salt to create a dry rub.
Pat fish fillets dry with paper towels; apply olive oil to all surfaces and coat evenly with the dry rub.
Preheat a grill or grill pan to medium-high heat (approximately 400°F/200°C).
In a mixing bowl, emulsify lime juice and sour cream, then toss with shredded cabbage and cilantro until thoroughly coated.
Place fish fillets on the grill grate and cook for 3 to 4 minutes per side, or until the internal temperature reaches 145°F (63°C).
Remove fish from heat and flake into large segments using a fork.
Toast corn tortillas on the grill for approximately 30 seconds per side until pliable and slightly charred.
Distribute flaked fish evenly among the tortillas and top with the prepared cabbage slaw.
Serve immediately with lime wedges.