In a small bowl ,whisk together the lime juice, vinegar, sesame oil, fish sauce (optional), salt, red pepper flakes, sesame seeds and mint. Stir in the garlic and chile and set aside.
To a medium sized bowl, add cooked shrimp, sliced cucumbers, cilantro, green onion and bell pepper. Pour dressing over and toss to combine. Serve with more cilantro and or mint leaves with sesame seeds sprinkled on top. Refrigerate covered if not eating right away.
Notes
If unable to find Japanese cucumbers, use a seedless variety with very thin skin, such as English or Persian cucumbers.