Cook rice noodles. Bring a large pot of water to a boil and cook noodles according to the package instructions. Once al dente, drain. When draining, reserve 1/2 cup of pasta water.
Make the sauce peanut butter sauce. Adjust according to taste and set aside.
When the water is almost boiling, start the chicken. Add oil to a large skillet over medium-low to medium heat and let it get hot. Add chicken, salt, and pepper and saute for 5-7 minutes, stirring occasionally, until browned. Remove from the pan, leaving the juices behind, and set aside.
Saute the veggies. Add broccoli, carrots, and salt and pepper in the same pan with the remaining chicken juices, and cook for 2-3 minutes, stirring occasionally. Then add peppers, stir to combine, and saute for another 5-7 minutes. Turn down the heat to low.
Drain and rinse the rice noodles, saving 1/2 cup of the pasta water.
Assemble. Add rice noodles, cooked chicken and its juices, peanut sauce, and 2 tablespoons of pasta water to the pan and toss to combine. Let warm through, about 1 minute. If desired, add more pasta water to thin out the sauce.
Top with optional toppings and enjoy.