Cook the rice noodles according to package instructions. Drain and set aside.
In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the sliced chicken and cook until browned and cooked through, about 5-7 minutes.
Add the minced garlic, red bell pepper, and snap peas to the skillet. Stir-fry for another 3-4 minutes until the vegetables are tender-crisp.
In a small bowl, whisk together the peanut butter, soy sauce, honey, rice vinegar, sesame oil, and red pepper flakes (if using) until smooth.
Add the cooked noodles and peanut sauce to the skillet. Toss everything together until the noodles are well coated and heated through, about 2-3 minutes.
Remove from heat and garnish with sliced green onions, chopped peanuts, and cilantro before serving.