Cook the pasta in plenty of rapidly simmering water according to package directions until al dente, then drain. Transfer to a large serving bowl.
Meanwhile, heat the oil in a large skillet. Add the garlic and bell pepper and sauté over medium heat until the garlic is lightly golden and the bell pepper is slightly wilted, about 3 to 4 minutes.
Add the spinach, tomatoes, chickpeas, sun-dried tomatoes, and oregano. Stir together and simmer gently for 8 to 10 minutes.
Combine the mixture from the skillet with the pasta and toss together.
Season with salt, pepper, and the optional red pepper flakes. Toss again, sprinkle with the fresh herbs and optional nuts, and serve.