Boil vermicelli according to package instructions. Drain, rinse with cool water, put in a bowl, and cover with a towel.
Set out herbs, cucumber, sprouts, and lime wedges on a platter. Set out cooked toppings on platters. Serve garnishes and dipping sauce in small bowls.
Before serving, check noodles; if gummy, rinse again and drain. Guests assemble their own salads: first noodles; then herbs (loosely torn), cucumber, and sprouts; then toppings; then garnishes and a drizzle of lime and/or dipping sauce.
Note: Nutritional analysis is per serving without topping.