Remove and discard seeds from peppers and tomatoes. Dice peppers and tomatoes; place in a large bowl. Toss in garlic, herbs, and, if desired, cheese.
Stir together oil, next 3 ingredients, and, if desired, sugar; add to tomato mixture, tossing to coat. Cover and chill 2 to 4 hours. Serve with a slotted spoon. Garnish, if desired.