Though dark cuts like thighs are higher in fat than white meat, they also have more iron and zinc.
Combine vinegar, honey, and a pinch of salt in a small bowl. Stir in onion. Let stand at room temperature, stirring occasionally, for at least 30 minutes.
Pulse peas, avocado, chopped cilantro, lime juice, jalapeño, garlic, 1/2 tsp. cumin, and 1/4 tsp. salt in a food processor until combined but not smooth. Transfer to a bowl, cover and refrigerate.
Mix 1 Tbsp. oil, chili powder, reminaing 1 tsp. cumin, and 1/2 tsp. salt in a small bowl. Rub chicken all over with spice mixture. Heat remaining 1 Tbsp. oil in a medium skillet over medium heat. Cook chicken, turning, until cooking through, about 12 minutes. Let rest for 5 minutes on a cutting board, then shred. Drain onion.
Fill tortillas with cabbage, pea quacamole, chicken, pickled onions, and additional toppings, if desired. Garnish with cilantro sprigs. Serve immediately.