Trim off and discard root ends of green onions. Cut off and slice green tops and set aside. In a food processor combine white parts of the green onions, the chicken breast, sweet pepper, 1 tablespoon of the vinegar, the hoisin sauce, the oil, black pepper and, if desired, crushed red pepper. Cover and pulse with several on-off turns until chicken mixture is finely chopped. Transfer to a medium bowl. Add cabbage and toss to combine.
Fill a large shallow plate that has a rim with water. Slide a rice paper wrap into the water and soak for 5 to 10 seconds. Slide out of the water and place on a clean surface. Place 1/8th of the filling into the center of the wrap and fold up the sides of the wrap and roll, enclosing the filling. Repeat with the remaining wraps and filling.
For the dipping sauce, in a small bowl combine sliced green onion tops, the remaining 2 tablespoons vinegar, the water, and soy sauce.