Whisk together soy sauce, sesame oil, lime juice, garlic powder, ground ginger, and chili flakes in a bowl. Add chicken thighs and toss to coat. Marinate for at least 20 minutes at room temperature or up to 4 hours in the refrigerator.

Make the peanut sauce by whisking together peanut butter, soy sauce, honey, rice vinegar, sesame oil, minced garlic, and grated ginger until smooth. Add warm water one tablespoon at a time until pourable. Set aside.

Prepare the slaw by combining both cabbages, carrots, red bell pepper, scallions, and cilantro in a large bowl. Add lime juice, rice vinegar, sugar, and a pinch of salt. Toss well and let sit for 10 minutes.

Heat a grill pan or skillet over medium-high heat with a drizzle of oil. Cook the marinated chicken thighs for 5 to 7 minutes per side until golden brown and cooked through to an internal temperature of 165 degrees F. Let rest 5 minutes then slice thinly.

Warm tortillas in a dry skillet for 30 seconds per side or in the microwave for 15 seconds. Spread peanut sauce on each tortilla, layer with slaw and sliced chicken, drizzle with more peanut sauce, and garnish with cilantro and peanuts if using.

Fold the sides in and roll tightly. Slice in half and serve immediately.