1. Whisk honey, vinegar, oil, 1/2 tsp. salt, and 1/4 tsp. pepper in a small bowl.
2. Set cheese pieces slightly apart in a wide, shallow bowl and drizzle with about 1 1/2 tbsp. dressing. Pit fruit and cut plums in half or peaches in quarters; put in a bowl and gently mix with 1 tbsp. dressing. In a large bowl, toss lettuces with dressing to coat.
3. Divide lettuces among 4 plates. Tuck in cheese, then arrange fruit on top. Scatter mint and pistachios over salads and serve extra dressing on the side. Season to taste with more salt and pepper.