In a medium bowl, combine the graham cracker crumbs and granulated sugar, mixing thoroughly. Pour in the melted butter and combine until the mixture resembles wet sand. Firmly press this mixture into the bottom and slightly up the sides of a 9-inch springform pan. Place the crust in the refrigerator to chill and set while you prepare the filling, about 30 minutes.

In a mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy, about 2 minutes. Gradually add in the marshmallow fluff and vanilla extract, mixing until well combined. Once smooth, gently fold in the thawed whipped topping until the filling is light and airy.

Remove the chilled crust from the refrigerator and spread the creamy filling evenly over it, smoothing the top with a spatula. Once spread evenly, cover the cheesecake with plastic wrap or foil and refrigerate for at least 4 hours or preferably overnight.

When ready to serve, remove the springform ring from the cheesecake. Decorate the top with fresh berries or mini marshmallows. Optionally, drizzle chocolate sauce or caramel over the cheesecake. Slice into wedges and serve chilled.