In medium bowl, stir together the shrimp, 2 teaspoons soy sauce, and 2 teaspoons cornstarch. Let it sit and marinate for 5 minutes.
In separate bowl, whisk together the remaining 4 teaspoons soy sauce, remaining 2 teaspoons cornstarch, rice vinegar, hoisin sauce, and ginger until the starch is dissolved.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat until shimmering. Add half of the marinated shrimp, and cook for 1 minute on each side, or until just cooked through. Transfer the shrimp to a clean bowl, and repeat with remaining shrimp. Wipe out the skillet with paper towel.
In the same pan, heat the remaining 2 tablespoons oil until shimmering. Add the red onion, bell pepper, and shishito peppers. Cook, stirring, for 2 to 4 minutes, until the peppers begin to blister. Add the vinegar mixture, and cook, stirring, for 1 to 2 minutes, or until the sauce is slightly thickened. Add the shrimp to the pan, and cook, tossing well until the shrimp and vegetables are coated with the sauce.
Fill the tortillas with the shrimp mixture, cabbage and green onions.
Recipe by Go Dairy Free at https://www.godairyfree.org/recipes/asian-fajitas-dairy-free