To prepare coleslaw: Combine sour cream, mayonnaise, cilantro, green onions, lime zest, lime juice, sugar, salt and pepper in a medium bowl; mix until smooth and creamy. Add cabbage and toss to combine. Refrigerate until ready to use and may be made up to 4 hours ahead.
To prepare fish: Combine chili powder, lime juice, oil, cumin, onion powder, garlic power, salt and pepper in a small bowl. Rub adobo rub all over fish. Let stand 20 to 30 minutes for the fish to absorb the flavor.
Preheat grill to medium-high. Oil the grill rack or use a grilling basket (which works best due to the tenacity of fish sticking to the grill). Grill the fish until it is cooked through and easily flakes with a fork, 3 to 5 minutes per side. Transfer the fish to a platter and separate into large chunks.
Serve the tacos family-style by passing the fish, tortillas, coleslaw and taco garnishes separately.