Combine chicken broth and saffron in a medium saucepan. Bring to a simmer and keep it warm over low heat. Do not boil.
Rise and pat dry the shrimp with a paper towel. Season with salt and pepper to taste. Set aside.
In a large paella pan, or a very large skillet, heat 2 tablespoons of oil over medium heat. Add chorizo to the skillet, sauté for 3 minutes, stirring occasionally. Remove from skillet and set aside.
Add chicken to the same skillet and cook for 5 minutes, or until lightly browned and cooked. Season with salt and pepper to taste. Add onion and red pepper; cook for 5 minutes, stirring occasionally. Add garlic; cook for 1 minute until fragrant.
Add uncooked paella rice; cook (toast) for 2 minutes, stirring constantly.
Stir in hot chicken broth, cooked chorizo, lemon juice, sweet paprika, and 2 tablespoons olive oil; mix to combine. Reduce heat to medium-low and bring to simmer; cook for about 10 minutes, or until the rice has absorbed most of the broth and is almost tender.
Scatter the peas over the rice. Reduce heat to low, cover with foil or a lid, and cook for 5 minutes.
After 5 minutes, arrange shrimp and roasted red pepper strips over the rice, cover, and continue cooking for 5 minutes, or until the rice is tender. Remove from heat and let stand, covered, for 10 minutes.
Garnish with chopped parsley. Serve with lemon, if desired.