Trim any excess fat from the chicken breasts and butterfly them for even cooking. In a small bowl, whisk together 1/4 cup balsamic vinegar, 2 tablespoons extra-virgin olive oil, 1 1/2 tablespoons Italian herb blend, 3/4 teaspoon salt, 1/2 teaspoon black pepper, and 1/2 teaspoon garlic powder to create the marinade. Place the chicken breasts in a bowl or zip-top bag, pour the marinade over the chicken, and toss to coat. Cover and refrigerate for at least 2 hours, or up to 24 hours for more flavor. I like to marinate the chicken overnight—you'll really taste the difference!
Preheat the grill to medium heat (about 450°F). Remove marinated chicken from the fridge and let excess marinade drip off; discard remaining marinade. Grill the chicken for 5 minutes on one side, then flip and grill for another 4-5 minutes, or until the thickest part reaches 165°F. Rest the grilled chicken for a few minutes before slicing into strips to keep it juicy.
In a small bowl or jar, combine 1/4 cup balsamic vinegar, 2 tablespoons apple cider vinegar, 2 tablespoons extra-virgin olive oil, 2 tablespoons water, 1 tablespoon honey, 1 tablespoon Dijon mustard, 1/4 teaspoon salt, and 1/8 teaspoon black pepper. Whisk or shake well until the dressing is fully emulsified. You can refrigerate this vinaigrette for up to a week—it's great to have on hand!
In a large serving bowl or meal prep container, layer the chopped romaine lettuce or mixed greens. Top with sliced grilled chicken (from Step 2), sliced strawberries, thinly sliced red onion, and crumbled goat cheese. Drizzle with the balsamic vinaigrette (from Step 3) just before serving. I like to add a little extra goat cheese on top for an extra creamy texture.