Cook the noodles: Cook the rice vermicelli noodles according to package directions. Rinse under cold water to stop cooking and prevent sticking. Drain well.
Prepare the vegetables: Slice the bell pepper, cucumber, and scallions. Shred the carrots. Chop the cilantro and peanuts.
Make the peanut sauce: In a medium bowl, whisk together peanut butter, soy sauce, lime juice, honey (or maple syrup), garlic, and ginger. Add water, 1 tablespoon at a time, until the sauce reaches your desired consistency.
Assemble the salad: In a large bowl, combine the cooked noodles, bell pepper, cucumber, carrots, scallions, and cilantro.
Add the sauce: Pour the peanut sauce over the noodle mixture and toss well to coat.
Add protein (optional): If using grilled chicken, shrimp, or tofu, add it to the salad and toss.
Garnish and serve: Garnish with chopped peanuts and any other optional toppings. Serve immediately or chill for later.