Season the sliced chicken thighs with the garlic powder, chili powder, and salt.
Heat 1 tablespoon of oil in a large skillet over medium heat. Add the seasoned chicken thighs to the skillet and cook for 2-3 minutes without moving the chicken. Flip and cook an additional 3-4 minutes, stirring occasionally, or until cooked through. Remove the chicken from the pan and set aside.
Heat the remaining oil in the skillet. Add the sliced pepper and sliced onion, and cook, stirring occasionally, until soft. This will take about 8-10 minutes.
Add the chicken back to the skillet and stir to combine.
While the peppers and onions are cooking, open the hoagie rolls and place cut-side-up on a sheet pan. Place provolone cheese on one side of the rolls.
Divide the chicken/pepper mixture evenly between one side of the hoagie rolls. Place the provolone cheese on the other side of each hoagie bun. Bake for 4-5 minutes, or until the cheese is melted.
Remove the sandwiches from the oven and drizzle the Cheez Whiz evenly over the chicken/pepper mixture. Close the sandwiches and serve while warm.