Preheat oven to 325°F (163°C). Line a 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal. Finely crush the graham crackers with a food processor or by transferring the graham crackers to a gallon-sized ziploc bag and crushing with a rolling pin.
Make the crust: In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Press mixture firmly into the bottom of the prepared pan. Bake for 10 minutes, then set aside to cool slightly.
Make the apple topping: Chop the apples. In a bowl, toss the chopped apples with cinnamon and brown sugar. Set aside.
Prepare the cheesecake filling and top with chopped apple mixture: Using an electric mixer, beat the cream cheese and sugar until smooth and creamy. Mix in the Greek yogurt, vanilla, and salt. Add the eggs one at a time, mixing on low speed until just combined. Stir in the flour until smooth. Spread the cheesecake mixture evenly over the cooled crust. Evenly spoon the apples over the cheesecake layer.
Prepare the streusel topping: Use a cheese grater to grate the cold butter (or cut into small cubes). In a small bowl, combine brown sugar, flour, and cinnamon. Add the cold grated butter and mix with a fork (or your fingers) until crumbly. Sprinkle the streusel evenly over the apples.
Bake: Transfer to the oven and bake for 40 minutes, or until the cheesecake is set in the center.
Cool & chill: Allow bars to cool completely at room temperature (about 30 minutes), then refrigerate for at least 3 hours (or overnight) before slicing.
Finish with caramel: Just before serving, drizzle caramel sauce over the top. Slice into bars and enjoy!