Bring 4 cups of water to a boil. Place noodles in a large bowl and cover with the boiling water. Allow noodles to soak for 5 minutes, drain, and rinse with cold, running water for 30 seconds. Drain well and set aside.
In a small bowl, combine the fish sauce, vinegar, sugar, red pepper, coconut milk, and if desired, the tamarind concentrate, stirring until the sugar is dissolved.
Heat the sesame and peanut oils in a wok or large saucepan over medium-high heat. Just before the oil is smoking, add the shrimp and cook until pink, stirring constantly. Add the tofu, mushrooms, bean sprouts, carrots, red bell pepper, garlic, and reserved noodles, and cook until heated through, about 2 minutes.
Pour the sauce mixture into the wok and toss until combined. Cook until the mixture is steaming and most of the liquid has evaporated. Add the peanuts and green onions and cook an additional 30 seconds.
Remove the wok from the heat and season with the lime juice and cilantro. Serve hot with Sriracha, if desired.