Mix the graham cracker crumbs, melted butter, granulated sugar, and salt in a bowl until evenly moistened.
Press the mixture firmly into a 9-inch pie plate or springform pan across the bottom and slightly up the sides.
Place the crust in the refrigerator to chill while preparing the filling.
Beat the softened cream cheese in a large bowl until smooth.
Add the marshmallow creme, powdered sugar, vanilla extract, lemon juice, and salt to the cream cheese.
Mix until the filling is thick, creamy, and fully blended.
In a separate bowl, whip 1 1/4 cups cold heavy whipping cream until stiff peaks form.
Gently fold the whipped cream into the cream cheese mixture until combined and light.
Spread the filling evenly into the chilled crust and smooth the top.
In a clean bowl, whip 1 cup cold heavy whipping cream with 2 tablespoons powdered sugar and 1/2 teaspoon vanilla extract until stiff peaks form.
Spoon or pipe the whipped cream over the cheesecake.
Add mini marshmallows and extra graham cracker crumbs on top if using.
Cover the cheesecake and refrigerate for at least 6 hours or overnight.
Slice with a sharp knife, wiping the blade clean between cuts for neat slices.