Combine shrimp, 2 T rice vinegar, and chili garlic sauce in a large bowl; toss well. Cover and chill 1 hour.
Combine remaining rice vinegar, oil, and next 6 ingredients (through salt)in a small bowl, stirring with whisk.
Place 2 C spinach on each plate; top each with 1 C shrimp mixture. Arrange 1/4 C mango, 1/4 C radishes, and 1 T avocado around shrimp on each plate. Top wach serving with 2 T green onions and 1 1/2 tsp sunflower seeds. Drizzle each salad with 2 T vinaigrette.