Preheat the grill to medium-high heat.
Pat the chicken breasts dry and brush with olive oil.
Season both sides with garlic powder, onion powder, paprika, salt, and black pepper.
Place the chicken on the grill and cook for 6 to 7 minutes per side until fully cooked and the internal temperature reaches 165°F (74°C).
While the chicken grills, whisk together the buffalo sauce, melted butter, and honey in a small bowl.
During the last few minutes of cooking, brush the buffalo sauce mixture generously over the chicken.
Remove the chicken from the grill and let it rest for 5 minutes.
Lightly toast the brioche buns on the grill.
Spread ranch dressing on the top and bottom buns.
Layer the grilled buffalo chicken onto each bun.
Top with lettuce, sliced red onion, and cheese if using.
Drizzle with additional buffalo sauce if desired and serve immediately.