Prep the marinade: In a bowl, whisk olive oil, lime juice, chili powder, cumin, smoked paprika, garlic powder, onion powder, oregano, salt, and pepper.
Marinate the chicken: Add chicken to a zip-top bag or bowl, pour in the marinade, and toss to coat. Rest 20–30 minutes at room temperature, or up to 8 hours in the fridge.
Make the slaw: Toss cabbage, cilantro, lime juice, olive oil, and salt.
Let it sit while you grill to soften slightly.
Stir the sauce: Mix sour cream (or yogurt), mayo, hot sauce or adobo, lime juice, and a pinch of salt until smooth. Adjust heat to taste.
Heat the grill: Preheat a gas or charcoal grill to medium-high (about 400–450°F). Oil the grates to prevent sticking.
For a grill pan, heat over medium-high and lightly oil.
Grill the chicken: Shake off excess marinade. Grill 5–7 minutes per side for thighs, 4–6 minutes per side for breasts, until the thickest part reaches 165°F. Let rest 5 minutes.
Warm the tortillas: Place tortillas on the grill 15–30 seconds per side until pliable and lightly charred.
Keep them wrapped in a clean towel to stay warm.
Slice the chicken: Cut into thin strips or small bite-size pieces. Squeeze fresh lime over the top and a pinch of salt if needed.
Assemble: Layer slaw on warm tortillas, add chicken, drizzle with sauce, and top with onion, cilantro, avocado, and cheese if using. Finish with lime.