In a medium bowl, combine the ground pork, fish sauce, brown sugar, soy sauce, garlic, shallot, black pepper, and 1 tablespoon oil. Mix gently just until combined. Shape into 16 small meatballs, about 1 1/2 inches (4 cm) wide, and place on a plate.
Stir the warm water, fish sauce, lime juice, sugar, garlic, and optional chile together in a bowl until the sugar dissolves. Taste and adjust with a little more lime for tartness or water for a milder sauce. Set aside.
Toss the carrot with rice vinegar, 1 teaspoon sugar, and salt. Set aside while you prepare the remaining components.
Cook the rice vermicelli according to the package directions until tender. Drain, rinse under cool water, and drain well. Divide the noodles among four bowls.
Heat a lightly oiled grill, grill pan, or large skillet over medium-high heat. Cook the pork meatballs, turning regularly, until browned and cooked through to an internal temperature of 160°F (71°C), about 10 to 12 minutes. Transfer to a clean plate.
Arrange lettuce, cucumber, pickled carrot, and herbs around the noodles. Add four meatballs to each bowl. Serve with the dipping sauce on the side or spoon it over each bowl just before eating.