Line a 9×13-inch pan with parchment, leaving overhang for lifting.
Stir graham crumbs, sugar, and melted butter until evenly moistened. Press firmly into the pan. Chill 15 minutes.
Bloom gelatin in cold water in a small bowl. Let stand 5 minutes.
Whip cold heavy cream to soft peaks and set aside.
Beat cream cheese, powdered sugar, sour cream, vanilla, and lemon juice until smooth and fluffy.
Warm the bloomed gelatin just until melted, then mix it into the cream cheese filling.
Fold whipped cream into the filling. Spread over the crust and smooth. Chill 30 minutes.
Cook peaches, preserves, cornstarch, cinnamon, and lemon zest in a saucepan over medium heat until glossy and slightly thick, 5–7 minutes. Cool completely.
Spoon cooled peach topping over set filling. Chill at least 4 hours, or until firm.
Lift out by the parchment and slice into 16 bars. Serve cold.