In a large mixing bowl, combine the softened cream cheese, Greek yogurt, powdered sugar, vanilla extract, and lemon juice. Beat with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes.
Gradually add the milk and protein powder to the mixture, continuing to mix until fully incorporated and fluffy, about 2 more minutes.
Taste the mixture and adjust sweetness if necessary by adding more powdered sugar.
Spoon the cheesecake fluff into serving bowls or glasses.
Chill in the refrigerator for at least 30 minutes to allow the flavors to meld and the texture to firm up.
Before serving, top with whipped topping and fresh berries if desired.