Make the garlic-chili oil: combine 1/2 cup olive oil, 4 crushed garlic cloves, and 2 tablespoons crushed red pepper flakes in a small saucepan and bring just to a low boil, then reduce to low and simmer 20–30 minutes; let cool.
Prepare the tomatoes: add sliced heirloom tomatoes and halved cherry tomatoes to a bowl or plate, drizzle with the cooled chili-garlic oil, and season with salt and pepper; set aside to serve with the finished dish.
Heat 2 tablespoons olive oil in a medium Dutch oven or large skillet over medium-high heat.
Cook the chicken: add the chicken pieces, 2–3 minced garlic cloves, 2 tablespoons balsamic vinegar, 1 tablespoon smoked paprika, and 1/2 teaspoon salt plus pepper to taste; toss to coat and cook until browned and cooked through, about 5 minutes.
Stir in the chopped oregano and cook 1 more minute, then transfer the chicken to a plate.
Cook the peppers: add another tablespoon olive oil to the same pan, add sliced bell peppers and a pinch of salt and pepper, and sear until edges begin to caramelize, about 3–4 minutes.
Add the orzo and another tablespoon olive oil to the peppers, stir to coat, then pour in 2 1/2 cups water; cook, stirring often, until most liquid is absorbed and orzo is creamy and tender, about 8–10 minutes.
If the orzo is still firm in the center, add another 1/2 cup water and continue cooking until soft, stirring frequently to prevent sticking.
Finish the dish: return the chicken and add the olives to the cooked orzo, remove from heat, and let warm through for about 3 minutes.
Serve: top the orzo and chicken with crumbled feta and serve with the tomatoes in chili garlic oil alongside.
