Beat cream cheese, egg, vanilla extract, and salt in a medium bowl with an electric mixer on medium speed until light and fluffy, 1 to 2 minutes.
Add sweetener, and beat until filling is smooth and fluffy, about 2 minutes. Spoon filling into cooled piecrust.
Prepare the Brown Sugar Filling
Whisk eggs until bright yellow and well combined.
Add low carb brown sugar, low carb corn syrup, bourbon, and vanilla extract. Whisk together until thickened and smooth.
Sprinkle chopped pecans over Cream Cheese Filling in piecrust.
Gently spoon Brown Sugar Filling over chopped pecans. Arrange pecan halves over Brown Sugar Filling.
Place pie on a baking sheet. Bake at 375°F for 10 minutes. Reduce oven temperature to 350°F, and bake until filling is puffed up and set and crust is golden brown, 30 to 35 minutes.
Transfer pie to a wire rack, and cool completely, 2 to 3 hours.
Prepare Whipped Cream
Pour the heavy cream into large bowl of a stand mixer fitted with wire whip. Beat on medium-high until cream forms soft peaks. Add erythritol and vanilla and continue beating until cream forms stiff peaks.
Transfer whipped cream to a piping bag with decorative tip and add whipped cream as desired. Top each dollop with a pecan half.