In a small non-reactive bowl, whisk together rice wine vinegar, miso, and sesame oil until well combined. Set aside.
In a medium size bowl, combine chicken, noodles, tomatoes, green beans, arugula or other salad greens, and cilantro. Drizzle miso vinaigrette over salad and toss until evenly coated. Taste and adjust seasoning. If using papayas, place half a papaya on each of 4 plates. Divide salad evenly among papaya halves or serve in cool Asian-style bowls if you're entertaining.