In a large bowl, whisk together the mayonnaise, lime juice, vinegar, garlic, Sriracha, sugar, and cilantro, mixing well. Stir in the red onion and slaw mix, combining until well-mixed. Refrigerate until use.
In a small dish, combine the cumin, chili powder, brown sugar, and salt; mix well. Rub the spice mix on the salmon (not skin).
Heat the olive oil in a large skillet over medium-high heat until shimmering. Place the fish in the hot skillet, skin side down, and cook for 4-5 minutes before turning over and cooking for 4 minutes on the other side. The fish will flake apart easily when done.
Fill each tortilla with 2½ ounces of salmon, about ¼ heaping cup slaw mix, and 1 tablespoon chopped cilantro; serve hot.