Marinate the chicken. Add the Dijon, 2 tbsp honey, juice of 1 lemon, 1 grated garlic clove, and olive oil to a large bowl or zip-top bag. Whisk to combine. Add the chicken and toss until completely coated. Marinate for at least 30 minutes and up to several hours in the refrigerator.
Make the peach salsa. Add the diced peaches, jalapeño, red onion, cilantro, red pepper, garlic, 1 grated garlic clove, 2 tablespoons lemon or lime juice and 1/2 teaspoon salt to a medium bowl. Gently toss to combine. Taste and adjust the seasoning if needed. Set aside while you grill the chicken.
Preheat the grill. Heat a gas or charcoal grill to medium-high heat. Clean the grates well and lightly oil them to prevent sticking. Alternately you can use an indoor grill pan or large cast-iron skillet or griddle. Heat to a medium-high heat until very hot.
Grill the chicken. Remove the chicken from the marinade and discard the remaining marinade and garlic. Pat the chicken dry with paper towels. Sprinkle both sides with 1 teaspoon salt. Grill the chicken until it easily releases from the grates and has nice grill marks, about 3–4 minutes. Flip and continue cooking for another 2–4 minutes, or until the chicken reaches an internal temperature of 165°F.
While the chicken grills, make the whipped feta. Add the feta, Greek yogurt, cream cheese, 2 tsp honey and 2 tsp lemon juice to a food processor. Blend until smooth and creamy, scraping down the sides as needed. Add water, a teaspoon at a time, until the feta is creamy and easily spreadable. Season to taste with salt and pepper. Set aside.
Rest the chicken. Transfer the grilled chicken to a plate and let it rest for about 5 minutes before serving.
Assemble. Arrange the chicken on a large platter. Dollop the feta on top of each piece of chicken. Spoon the peach salsa generously over the chicken. Serve immediately. Serve with extra whipped feta and mango salsa. Serve with crusty bread!