For the batter, place flour, baking powder and salt in a large bowl and whisk in wine and seltzer. Let stand 30-60 minutes.
Place seafood on a large towel-lined sheet pan.
Heat oil in a large Dutch oven or tabletop fryer to 365°F. Place flour, salt, pepper and Old Bay in shallow dish for dredging and set near fryer or the stove. Set up a rack topped with paper towels over baking sheet to remove fried seafood to.
Working in small batches, dredge some of the fish, shrimp and calamari lightly then dip in batter just before adding to the hot oil. Fry to crisp and golden brown; remove and drain on paper towel-lined rack. Sprinkle with flaky sea salt and a little chili flake.
When all of the seafood is done, dredge squash and zucchini, coat in batter and fry to golden. Lastly, fry herbs and sliced lemon the same way until crisp. As foods come out of hot oil, sprinkle with sea salt and chili flakes.
Arrange piles of seafood and veggies on parchment or butcher paper or on a large cutting board. Scatter fried herbs and lemon slices among the seafood and place lemon wedges alongside. Pass hot sauce at the table.
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