Whisk fish sauce, lime juice, sugar, garlic, and chili in a bowl until sugar dissolves. Set dressing aside.
Season pork with 1 tbsp oil, salt, and pepper. Heat grill or grill pan over medium-high heat.
Grill pork 3–4 minutes per side until cooked through. Rest 5 minutes, then thinly slice.
Cook noodles per package, drain, rinse under cold water, and drain well.
Toss noodles with 1 tbsp dressing. Arrange greens, carrots, cucumber, herbs, and noodles in bowls.
Top with sliced pork and peanuts. Drizzle remaining dressing over each bowl.