Make Sriracha yogurt sauce - If prepping right before cooking, get oven heating before continuing with prep. Whisk together yogurt, Sriracha, and first part of lime juice. (Can be done up to 5 days ahead)
Dress slaw - Combine coleslaw mix with second part of lime juice, oil (portion for tacos), and sugar. (Can be done up to 2 days ahead)
Line a sheet pan with foil and brush with some oil. Spread fish out in a single layer.
Melt butter and combine with salt, garlic powder, and panko. Gently press panko crust onto fish strips.
Bake fish until cooked through, 9 to 11 minutes.
While fish is baking, in a large mixing bowl whisk together mustard, vinegar, and paprika. Add oil (portion for salad) while whisking. Top vinaigrette with tomatoes, spinach, and pepitas. Wait to toss until right before serving.
Slice limes into wedges and chop cilantro.
Warm tortillas according to package instructions.
Taste slaw and season to taste with some salt and pepper.
Fill tortillas with slaw, fish, and avocados. Top with Sriracha yogurt sauce and cilantro and serve with lime wedges. Enjoy with salad on the side.