PICKLE THE VEGETABLES: In a small bowl or jar, stir together rice vinegar, water, sugar, and fine salt until sugar dissolves. Add carrot and daikon matchsticks, press down into liquid, and let stand at least 30 minutes. For brightest flavor and best texture, refrigerate several hours or overnight.
MAKE THE MEATBALLS: In medium bowl, combine fish sauce, soy sauce, sugar, minced garlic, and finely minced green onions. Add ground pork and gently mix until evenly combined without overworking. Form into small meatballs about 1 to 1 1/4 inches in diameter (18-22 meatballs).
BROWN THE MEATBALLS: Heat neutral oil in large skillet over medium heat. Add meatballs in single layer and cook, turning occasionally, until browned on outside. Transfer to rimmed baking sheet and finish in 325°F oven until just cooked through, then set aside. Pour off and reserve most of the fat from pan for the broth.
DEGLAZE THE PAN: Add small splash of chicken broth to hot skillet and scrape up any browned bits from bottom. Set this deglazing liquid aside to add to soup pot.
START THE BROTH BASE: In Dutch oven or soup pot, heat 2 teaspoons reserved meatball fat (or neutral oil) over medium heat. Add sliced green onion whites, lightly smashed garlic cloves, and ginger slices if using. Cook, stirring, until fragrant and just beginning to turn golden at edges.
BUILD THE RICH BROTH: Add chicken broth and deglazing liquid from meatball pan. Stir in fish sauce, soy sauce, sugar, and Maggi seasoning. Bring just up to gentle simmer and cook 10-15 minutes so aromatics can infuse the broth.
ADJUST AND ENRICH: Taste broth and adjust seasoning, adding more fish sauce for salt and depth, pinch more sugar if it tastes sharp. Add little extra Maggi for savory intensity. If you prefer smoother broth, lift out garlic and ginger pieces. Slide browned meatballs into simmering broth and let them heat gently for several minutes so flavors meld. Turn off heat and stir in butter until melted.
COOK THE NOODLES: While broth simmers, cook rice noodles in separate pot of boiling water according to package directions just until tender. Drain and rinse briefly under warm water to prevent sticking. Divide cooked noodles among four warm soup bowls.
MAKE THE GARLIC BAGUETTE DUNKERS: Brush baguette slices with olive oil, rub or top with little grated garlic, and sprinkle with pinch of salt. Toast in skillet or 375°F oven until crisp and lightly golden. Set aside for serving.
ASSEMBLE THE BOWLS: Drain pickled carrots and daikon, reserving spoonful or two of brine if you like extra tang. Place about 1 tablespoon smooth pate in bottom of each noodle-filled bowl. Ladle in some of the very hot broth and whisk lightly so pate melts into liquid.
FINISH AND SERVE: Add several meatballs to each bowl along with more broth. Top with small mound of drained pickled vegetables, then sprinkle with cilantro and sliced green onions. Add few torn Thai basil leaves if you have them. Garnish each bowl with lime wedge and, if desired, few slices of jalapeño or tiny drizzle of mild chili oil. Serve immediately with garlic baguette dunkers on side for dipping.