Stir together the mayonnaise and sriracha. Refrigerate until ready to use.
In a large bowl, combine the ground turkey, garlic, green onions, soy sauce, cornstarch, and black pepper. Mix just until combined.
Shape the mixture into 20 small meatballs and flatten slightly.
Heat the oil in a large frying pan over medium heat. Add the meatballs in a single layer, working in batches if needed. Cook for 10–12 minutes, turning occasionally, until browned and the internal temperature reaches 165°F.
Meanwhile, cook the rice noodles according to the package directions. Drain and rinse with cold water.
Divide the lettuce and noodles among four bowls.
Top the noodles and lettuce with the turkey meatballs, pickled carrots and daikon, cucumber, cilantro, and optional jalapeño.
Drizzle with sriracha mayo and serve with lime wedges.