Whisk Dijon mustard, cider vinegar, rice vinegar, salt, sugar, and cayenne together in a large bowl for about 30 seconds. Whisk in olive oil in 1-teaspoon increments until emulsified. Whisk in tarragon, dill, parsley, chives, and thyme. Remove and reserve 1/2 of the dressing in a separate small bowl. Bring a large pot of lightly salted water to a boil; cook rotini at a boil until tender yet firm to the bite, about 8 minutes. Add snow peas, carrots, peas, and broccoli about 2 minutes before the pasta is done. Drain pasta and veggies well, but do not rinse. Transfer hot pasta mixture to the vinaigrette in the large mixing bowl and toss well to combine. Let rest for 5 minutes and toss again. Toss occasionally until the mixture is almost room temperature, 15 to 20 minutes. Add bell peppers, cherry tomatoes, red onion, green onions, salt, and the reserved dressing and toss well. Wrap and chill in the refrigerator for 3 to 4 hours before serving. Toss and adjust seasoning before serving.