In a large bowl, whisk the all-purpose flour and the rice flour with the egg, seltzer, toasted sesame oil and 3/4 teaspoon of salt. Add the kimchi, shrimp, squid and scallions to the batter.
In 2 medium nonstick skillets, heat 1/4 inch of vegetable oil. Spoon 2 mounds of the batter into each skillet and gently spread them into 4- to 5-inch rounds; be sure to evenly distribute the seafood in the pancakes. Cook over moderately high heat until the pancakes are golden and crisp on the bottom, 4 to 5 minutes. Carefully flip and cook over moderate heat until the pancakes are golden and crisp and the batter is cooked through, about 3 minutes longer. Using a slotted spatula, transfer the pancakes to a paper towel-lined plate to drain.
In a small bowl, combine the soy sauce and rice vinegar. Cut the seafood pancakes into wedges and serve them with the dipping sauce.