6-24 hours before dinner, marinate the chicken in the soy sauce and peanut sauce. Place the marinated breasts on a foil-lined pan, and broil both sides until slightly charred.
Toss the shredded carrot in a small bowl with the rice vinegar, water, and sugar. In another small bowl, prepare the dressing by mixing together the lime juice, sugar, water, soy sauce, and garlic/pepper if using.
Cook the rice noodles according to the package's instructions (for fresh, boil in water for ~1.5 minutes). Drain the noodles and run under cold water before distributing into serving bowls. Top with carrot, lettuce, herbs, sliced chicken and dressing.