Prepare the taco sauce by whisking together the sour cream, mayonnaise, lime juice, lime zest, minced cilantro, garlic powder, cumin, smoked paprika, and sriracha in a small bowl until homogenous. Cover and refrigerate for at least 15 minutes to allow flavors to meld.
In a medium mixing bowl, toss the shredded cabbage with a splash of lime juice and a pinch of salt to create the slaw base. Set aside.
Pat the fish fillets dry with paper towels to ensure optimal searing. Season both sides of the fish strips uniformly with salt, pepper, and additional cumin or taco seasoning if desired.
Heat the oil in a large non-stick skillet over medium-high heat. Once the oil is shimmering, add the fish strips in a single layer, ensuring not to overcrowd the pan.
Sear the fish for 3 to 4 minutes per side until the exterior is golden-brown and the internal temperature reaches 145°F (63°C) or the flesh flakes easily with a fork.
While the fish cooks, warm the corn tortillas in a dry skillet or over an open gas flame for 30 seconds per side until pliable and slightly charred.
Assemble the tacos by placing 2-3 strips of fish onto each warm tortilla. Top with a handful of cabbage slaw and a generous drizzle of the chilled taco sauce. Serve immediately with extra lime wedges.