Cook rice according to package instructions.
Meanwhile, in a small bowl, combine garlic powder, onion powder, ¾ tsp. salt, and ¼ tsp. pepper. In a large skillet over medium heat, heat oil. Season chicken all over with spice mixture and cook, turning occasionally, until golden brown and an instant-read thermometer inserted into thickest part registers 165°, about 7 minutes per side. Transfer to a cutting board. Remove skillet from heat.
In a large bowl, combine cabbage and carrots. In a medium bowl, whisk yogurt, vinegar, mustard, and sugar; season with ½ tsp. salt and ¼ tsp. pepper. Pour over cabbage mixture and toss to combine.
Cut chicken into bite-sized pieces. Return to skillet along with beans and BBQ sauce. Bring to a simmer over medium-low heat and cook, stirring occasionally to coat chicken, until sauce thickens, 2 to 3 minutes; season with salt and pepper.
Divide rice among bowls. Top with chicken mixture, coleslaw, corn, and pickles. Drizzle with BBQ sauce and sprinkle with scallions.