Whisk the tamarind paste, fish sauce, soy sauce, rice vinegar, and brown sugar together in a small bowl until smooth; set the sauce aside.
Bring 4 cups of water to a boil in a large pot. Add the rice noodles and cook about 5 minutes until very soft, stirring occasionally. Drain and rinse under cool water, then set aside.
Heat the vegetable oil in a wok or large skillet over high heat. Add the onion and stir-fry 2 minutes until starting to soften. Add the minced garlic and cook 30 seconds more, stirring frequently.
Add the chicken strips and tofu cubes to the wok and cook 2–4 minutes, stirring, until the chicken is just cooked through.
Push the chicken and tofu to one side of the wok. Crack the eggs into the empty side and scramble them with a spatula until just cooked, then mix them together with the chicken and tofu.
Stir in half of the bean sprouts, then add the cooked rice noodles and toss to combine. Cook about 1 minute, stirring constantly so everything is evenly mixed.
Pour the prepared sauce over the noodles, add half of the chopped peanuts and the scallions, then stir and cook 1–2 minutes until heated through. Stir in the sriracha to taste.
Serve immediately, garnishing with the remaining peanuts and bean sprouts and lime wedges on the side.
