IPhone Xs lags/stutters

I recently upgraded iPhone 7 to a iPhone Xs, and found that the phone lags quite frequently over app/games that didn’t use to when I was using the iphone 7. Even the most basic of apps, whatsapp, I’m getting mini lags/stutters when I receive or send messages. My casual gaming sessions never once lagged when I was using the iPhone 7 but the frame rate drops in this new iPhone Xs is very disappointing and frustrating.

I’ve logged this case with Apple, who told me to do factory resets (which I have done and improved the performance very slightly), but I still face the lags. Anyone else facing the same problem?