Step 1: In a large bowl, combine the softened cream cheese and white sugar. Use an electric mixer (handheld or stand mixer) on medium speed to beat the cream cheese and sugar until smooth and creamy. This step is crucial for creating a lump-free filling. If you don't have an electric mixer, you can use a whisk, but it will require more effort. Make sure the cream cheese is properly softened; otherwise, you will end up with a lumpy filling. Continue mixing until the mixture is light and fluffy.

Step 2: Gently fold in the thawed Cool Whip. Use a spatula to gently fold the Cool Whip into the cream cheese mixture until just combined. Be careful not to overmix, as this can deflate the Cool Whip and make the filling less airy. Folding ensures that the filling remains light and fluffy. Incorporate all of the Cool Whip until you get a uniform mixture.

Step 3: Add the sliced strawberries, blueberries, and raspberries to the bowl.

Step 4: Gently fold the berries into the cheesecake filling. Use a spatula to carefully fold the berries into the filling, ensuring they are evenly distributed throughout the mixture. Be gentle to avoid crushing the berries.

Step 5: Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to allow the flavors to meld together. While not strictly necessary, chilling the salad for a short period enhances the flavors and allows the filling to firm up slightly. This makes it easier to serve and prevents the berries from sinking to the bottom. The salad can be prepared up to 24 hours in advance.