Place rice noodles in a large bowl and pour boiling water over them. Let soak for about 8-10 minutes, stirring occasionally. You want the noodles to soften, but still be firm.
Heat a wok or large skillet over medium-high heat and add 1 Tbsp vegetable oil. Add chicken to pan and let cook for about 5-7 minutes, until cooked through. When done cooking, move chicken to a plate.
While chicken is cooking, mix together lime juice, fish sauce, soy sauce, peanut butter, sriracha, tamarind concentrate, and sugar in a small bowl.
Add remaining Tbsp vegetable oil to the skillet and cook red Thai chili peppers and red bell peppers over medium-high heat for 2 minutes. Add shredded carrots and garlic and cook for another minute.
Reduce heat to medium, move veggies to the side of the pan, and pour the eggs into the pan. Cook, stirring the eggs until they're just getting scrambled.
Add the noodles, cooked chicken, and bean sprouts to the pan; pour in the sauce; and mix everything together. Cook for about a minute, until everything is heated through.
Serve Chicken Pad Thai in bowls with additional Thai peppers, scallions, peanuts, and cilantro for garnish.