Pickle Red Onions: Place red onions in a medium heat-proof bowl. In a medium pot, combine vinegar, 1/2 cup water, sugar, and salt; bring to a boil. Turn off heat and pour vinegar mixture over red onions. Let sit for at least 30 minutes (or up to 2 hours) at room temperature.
Cook Quinoa: Using the same pot, combine quinoa, vegetable broth, and a pinch of salt; bring to a boil. Reduce heat to low, cover, and cook until quinoa is fluffy and liquid is absorbed, about 15 to 18 minutes. Remove from heat, stir, and place lid back on to let grains steam until you're ready to assemble the bowls.
Prepare Yogurt Ranch: In a medium bowl, combine Greek yogurt, mayo, lemon juice, chives, dill, garlic powder, onion powder, salt, and pepper; mix to combine.
Sauté Chickpeas: Heat oil in a medium skillet over medium heat. Once hot, add chickpeas and cook for 4 to 5 minutes, stirring only occasionally until slightly crisp. Season with smoked paprika, garlic powder, and a pinch of salt. Add BBQ sauce and cook 1 to 2 more minutes allowing sauce to glaze over chickpeas.
Assemble Bowls: Divide quinoa mixture evenly between three bowls. Top with BBQ chickpeas, fire-roasted corn, pickled red onion, sharp cheddar, and avocado. Drizzle yogurt ranch dressing over top, and garnish with fresh chopped chives if desired.