Make the cucumber-edamame salad: In a medium bowl whisk together 3 tablespoons soy sauce, 3 tablespoons rice vinegar, 3 tablespoons sugar, 1 tablespoon sesame oil, and 1/2 teaspoon sriracha (if using) until the sugar dissolves.
Add the diced seeded cucumber, 1 cup cooked edamame, sliced scallions, and 2 teaspoons grated ginger to the dressing and toss to combine; let sit while you prepare the rest of the meal.
Make the sriracha mayo: In a small bowl stir together 1/2 cup mayonnaise and 2 tablespoons sriracha until smooth; taste and adjust if desired, then set aside.
Prep the chicken: If needed, flatten each chicken tender with your palm to about 1/4-inch thickness and trim any tendons. Season both sides with 3/4 teaspoon salt.
Set up a breading station: place 1/2 cup flour in one shallow bowl, the beaten eggs in a second, and 2 cups panko in a third. Dredge each seasoned tender in flour (shake off excess), dip in egg, then press into panko to coat fully; transfer to a plate.
Cook the chicken: Heat about 1/8 inch vegetable oil in a large nonstick skillet over medium heat. When hot, add the tenders in a single layer (work in batches if needed) and cook until golden and cooked through, 2–3 minutes per side.
Transfer cooked chicken to a paper towel–lined plate to drain briefly, then slice if desired.
Assemble bowls: Divide 4 cups cooked rice among 4 bowls. Dice the avocado and fold it into the cucumber-edamame salad. Place chicken on top of the rice with a generous spoonful of the salad alongside (to keep the breading crisp).
Finish and serve: Spoon some of the salad dressing over the rice as a sauce, drizzle with sriracha mayo, and sprinkle with sesame seeds if using. Serve immediately and pass extra salad and mayo at the table.