Heat the olive oil in a wide Dutch oven or deep skillet over medium heat. Add the onion and bell pepper. Cook, stirring occasionally, until softened, about 6 to 8 minutes. Stir in the garlic and cook for 30 seconds.
Add the potatoes, diced tomatoes and their juices, stock, wine, sweet paprika, smoked paprika, bay leaf, salt, and black pepper. Gently stir, bring the liquid to a simmer, then cover and cook until the potatoes are nearly tender, about 15 to 18 minutes.
Nestle the fish pieces into the simmering broth. Cover and cook gently for 5 minutes. Do not stir vigorously, as the fish can break apart.
Add the shrimp, cover, and cook until the shrimp are pink and opaque and the fish flakes easily, about 3 to 5 minutes more. The thickest pieces of fish should reach 145°F (63°C).
Remove and discard the bay leaf. Stir in the parsley and lemon juice. Taste the broth and add more salt or pepper if needed. Serve hot with lemon wedges and crusty bread, if desired.