Dressing the hot potatoes with a splash of vinegar ensures the salad has flavor throughout. Sweet red bell peppers and sugar snap peas lend color and improve the nutritional profile. This dish can be made eight hours ahead and chilled.
Place the potatoes in a large saucepan; cover with water. Bring to a boil. Reduce heat, and simmer 12 minutes or until tender; drain. Place potatoes in a large bowl. Add 2 tablespoons white wine vinegar, and toss gently. Cool completely.
Chop egg whites (reserve yolks for another use); set aside.
Combine remaining 2 teaspoons vinegar, mayonnaise, and next 5 ingredients (through salt) in a small bowl; stir with a whisk. Add vinegar mixture, egg whites, red onion, and remaining ingredients to potato mixture, stirring gently to coat.