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

Combine peanut butter, soy sauce, honey, rice vinegar, sesame oil, minced garlic, and grated ginger in a small bowl. Whisk until completely smooth. Add warm water one tablespoon at a time until the sauce is pourable but not watery. It should coat the back of a spoon nicely.

Toss green cabbage, red cabbage, carrots, bell pepper, scallions, and cilantro in a large bowl. In a small bowl, whisk lime juice, rice vinegar, sugar, and a pinch of salt. Pour over vegetables and toss well. Let slaw sit for 10 minutes to allow flavors to develop.

Heat a grill pan or large skillet over medium-high heat. Add a small drizzle of oil. Cook marinated chicken thighs 5 to 7 minutes per side without moving them, until golden and the internal temperature reaches 165 degrees F. Rest for 5 minutes on a cutting board, then slice thinly against the grain.

Warm tortillas in a dry skillet for 10 seconds per side until soft and pliable. Spread a generous spoonful of peanut sauce down the center of each tortilla, leaving about one inch free on each end.

Drain any excess liquid from the slaw. Layer slaw over the sauce, then top with sliced chicken. Drizzle with extra peanut sauce and sprinkle with chopped peanuts and cilantro if desired. Fold the bottom up, tuck in the sides, and roll tightly. Slice diagonally and serve immediately.