In a medium bowl, combine 1 tablespoon fish sauce, 1 tablespoon ginger, 2 teaspoons brown sugar, 1 teaspoon salt and ¼ teaspoon pepper.
Place sirloin tips between 2 sheets of plastic wrap and, using a meat mallet, gently pound them to an even ½-inch thickness. Add the beef to the fish sauce mixture and turn to coat. Marinate at room temperature for 15 minutes.
Bring a large pot of water to a boil. Add the noodles and immediately remove the pot from the heat. Let the noodles stand, stirring 2 or 3 times, until tender, 3 to 5 minutes. Drain in a colander, rinse under cold water and drain again. Transfer to a large bowl and set aside.
In a small bowl, whisk together the remaining ¼ cup fish sauce, 1 tablespoon ginger and 3 tablespoons brown sugar, the lime juice, 2 tablespoons water and chili-garlic sauce until the sugar dissolves. In a 12-inch nonstick skillet over medium-high, heat the oil until just smoking. Add the beef and cook until browned on both sides, turning once, about 6 minutes. Transfer to a plate and let rest for 5 minutes.
Meanwhile, to the noodles, add ½ cup of the lime juice mixture, the mint, cilantro and peanuts; toss to combine. Transfer to a serving platter or individual bowls. Cut each piece of meat into thirds with the grain, then slice as thinly as possible against the grain. Place the slices on top of the noodles and drizzle with the accumulated juices. Serve with the remaining lime juice mixture on the side.