Preheat the oven to 200 degrees F. Place a rack on a large rimmed baking sheet.
Put the panko and flour in separate shallow bowls. In another shallow bowl, beat the eggs. Season the fish fillets with salt and pepper. Dredge the fish in the flour, then dip in the egg, letting the excess drip back into the bowl. Coat in the panko. Transfer to a plate.
In a large skillet, heat 1/2 inch of oil over medium-high heat. Add the fish to the skillet (work in batches if necessary) and cook until the fish is browned around the edges, 3 to 4 minutes. Carefully flip the fish and fry until browned on the other side, 2 to 3 minutes more. Transfer to the rack on the baking sheet, season with salt, and place in the oven to keep warm.
Pour off all but 2 tablespoons of fat from the skillet. Add the bacon and cook over medium-high heat, stirring, until browned and crisp, about 6 minutes. Remove from the heat and stir in the shallot, vinegar and mustard.
In a large bowl, toss the lettuces and herbs with the bacon vinaigrette. Season the salad with salt and pepper. Serve the flounder with the salad and lemon wedges.