1) Cook noodles according to package directions. Drain and rinse with cold water until completely cool. (If using dried linguine instead of fresh Chinese noodles, cook it just until al dente since it will continue to soften as it sits.)
2) For the dressing, whisk together soy sauce, rice vinegar, sesame oil, peanut butter, honey, ginger, garlic, and red pepper flakes until smooth. (set aside if you're making 1-2 days ahead)
3) In a large bowl, toss the cooled noodles with the dressing until well coated.
4) Add cucumber, carrots, bell pepper, scallions, and cilantro. Toss gently to combine.
5) Cover and refrigerate for at least 2 hours, or preferably overnight.
6) Just before serving, garnish with sesame seeds and chopped peanuts.