In a small bowl, combine the garlic powder, smoked paprika, kosher salt, and black pepper. Rub the seasoning mixture onto both sides of the boneless, skinless chicken breasts.
Grill the dry-rubbed chicken over medium-high heat for 5-6 minutes per side or until the internal temperature is 165 degrees.
Meanwhile, combine all of the ingredients for the avocado ranch in your food processor or blender. Process until smooth, stopping to scrape down the sides as necessary.
Remove the chicken from the grill and cut into thin strips. Top each tortilla with chicken, bacon, lettuce, tomato, and feta cheese. Drizzle with the avocado ranch.