Lightly spray a 9x13-inch baking dish with nonstick spray or brush with a thin layer of melted butter. For very clean edges, line with parchment paper, leaving some overhang on the long sides as handles.

In a medium bowl, combine the graham cracker crumbs, granulated sugar, and fine sea salt. Pour in the melted butter and mix with a fork until the crumbs are evenly coated and the mixture resembles damp sand. It should clump when squeezed; if too dry, add about 1 tablespoon more melted butter.

Pour the crumb mixture into the prepared pan. Spread evenly and press firmly using your fingers or the bottom of a measuring cup or glass, making sure to press well into the corners. Refrigerate for at least 20–30 minutes to firm up while you prepare the cream cheese layer.

In a clean, cold bowl, beat 1 cup cold heavy whipping cream with a hand mixer on medium-high speed until medium peaks form—soft but holding their shape on the beaters. Do not overbeat. Refrigerate the whipped cream until ready to fold into the cream cheese mixture. If using whipped topping instead, simply measure 1 1/2 cups and keep chilled.

In a large bowl, beat the softened cream cheese on medium speed until smooth and fluffy, 1–2 minutes, scraping down the bowl as needed. Add the sifted powdered sugar, vanilla extract, and a pinch of salt. Beat on low to combine, then on medium until very smooth and creamy with no lumps.

Using a rubber spatula, gently fold the whipped cream into the cream cheese mixture in two or three additions. Use light, sweeping motions to keep the mixture airy. Fold just until smooth and uniform.

Remove the chilled crust from the refrigerator. Drop spoonfuls of the cream cheese mixture over the crust, then gently spread into an even layer with an offset spatula or the back of a spoon, taking care not to disturb the crust. Chill for 20–30 minutes to let this layer firm slightly.

In a small bowl, gently stir the blueberry pie filling to loosen it. If using, fold in the lemon zest. Spoon the blueberry filling over the cream cheese layer in small dollops, then carefully spread into an even layer without disturbing the cream layer too much.

In a cold bowl, beat 1 1/4 cups heavy whipping cream with 2 tablespoons powdered sugar and 1/2 teaspoon vanilla extract until medium-firm peaks form—thick and billowy but not grainy. If using whipped topping, gently fold in the powdered sugar and vanilla to flavor it slightly.

Gently spread the whipped cream mixture over the blueberry layer, making soft swoops or smoothing it flat as desired. Cover the pan tightly with plastic wrap or foil and refrigerate for at least 4 hours, preferably overnight, until the layers are fully set.

Just before serving, garnish the top with fresh blueberries, lemon zest curls, and/or crushed graham crackers or shortbread crumbs. Dust lightly with powdered sugar if desired. Slice into squares and serve chilled.