Cook pasta al dente according to package instructions in a large pot of generously salted water. Cook peeled and deveined shrimp or chicken in 2 T sesame oil in a skillet. Meanwhile, in a separate mixing bowl, combine soy sauce, garlic, vinegar, 1 T sesame oil, and sriracha (or hot chili oil). Whisk until combined. When the pasta is ready, drain it. Then immediately toss with the meat and dressing and 1/2 cup green onions until the pasta is evenly coated with the dressing. Prepare salad. Serve immediately, topped with extra garnishes if desired.