In a bowl, whisk olive oil, balsamic vinegar, garlic, Italian herbs, smoked paprika, salt, and pepper. Add chicken breasts and coat well. Marinate for at least 30 minutes or overnight.
Preheat oven to 400°F (200°C). Bake marinated chicken for 20–25 minutes or until internal temperature reaches 165°F. Rest for 5–10 minutes, then slice.
Whisk balsamic vinegar, honey, Dijon mustard, salt, and pepper. Slowly add olive oil while whisking until smooth.
Prepare vegetables by halving tomatoes, slicing avocado, and draining mozzarella.
Assemble salad with spinach, sliced chicken, tomatoes, avocado, and mozzarella.
Drizzle with vinaigrette before serving. This Baked Marinated Chicken Salad with Mozzarella and Balsamic Vinaigrette is best served fresh.