Prepare the slaw and sauce: Place the cabbage in a medium mixing bowl. In a separate large bowl, stir together the Greek yogurt, oil, garlic, and salt. Scoop about half of the yogurt mixture into the bowl with the cabbage. To the cabbage bowl, add the lime zest and juice. Stir to combine, then refrigerate until ready to serve.
To the bowl with the remaining Greek yogurt mixture, add the Thai sweet chili sauce, sriracha, and vinegar. Set aside.
Prepare the shrimp: Pat the shrimp dry and place in a large ziptop bag. Sprinkle in the cornstarch, then seal the bag and toss the shrimp to coat.
In a high-sided skillet, wok, or dutch oven, heat the 3 tablespoons oil over medium high. Once the oil is hot and shimmering, carefully add the shrimp, shaking off as much excess cornstarch as you can. Sauté, stirring almost constantly, until the shrimp is cooked through and the cornstarch is no longer white, about 4 minutes. Do not overcook, and if the shrimp looks dry, drizzle in extra oil as needed. Transfer the shrimp to the bowl with the Greek yogurt/Thai chili mixture and toss to coat the shrimp in the sauce.
Warm the tortillas (optional) and assemble the tacos: If you like, warm the tortillas in the microwave (put them in a stack and cover them with a lightly damp towel) or a 250 degree F oven. To serve, fill the tortillas with your desired number of shrimp and the slaw, then top generously with the slaw and green onions. Enjoy immediately.
Bang Bang Shrimp are best enjoyed the day they are made, so I recommend only sautéing the amount of shrimp you plan to eat that meal. The slaw can be refrigerated for 2 to 3 days, so you can make a larger batch of it in advance, then cook the shrimp just before serving.