Add the vegan sour cream, vegan mayo, mustard, lemon juice, salt, black pepper, and red pepper flakes to a large bowl. Add the cucumber, cooked green peas, red onion, and bell pepper.
¾ cup vegan sour cream, 2 tbsp vegan mayo, 1 tbsp mustard, 2 tbsp lemon juice, ¼ tsp salt, ¼ tsp black pepper, ⅛ tsp red pepper flakes, optional, ½ cup cooked green peas, 1 small red onion, finely chopped, 1 small cucumber, diced, 1 small bell pepper, diced