In a bowl whisk the vinegar and sugar together until dissolved. Mix in the cabbage mix and season with salt and pepper. Set aside. Before serving drain well.
In a shallow bowl, mix the garlic powder, paprika, oregano, flour, cornstarch, salt and pepper. Coat the shrimp in the mixture, then into the egg, then back into the flour mixture and coat very well.
Heat the canola oil in a non-stick pan or cast iron skillet over medium heat.
Once the oil is hot, working in batches if needed, fry the shrimp until golden brown and crispy, to an internal temperature of 120°F is reached. (To check the internal temperature, carefully remove a piece of shrimp from the oil onto a paper towel and probe the fattest part with a thermometer.)
Once cooked, set on a paper towel to drain any excess oil. Season with salt immediately.
In a bowl, mix the mayo, relish, lemon juice, and mustard. Season with salt and pepper. Taste and adjust any of the ingredients as needed.
Lightly toast the rolls. Spread the mayo on both halves of the roll. Layer the roll with cabbage mix and tomato seasoned with salt, pepper, and oregano, and shrimp.
Cut in half and serve with chips and pickles.