After the update to Pie the first think what I saw different was the coming of the new Navigation bar with only two buttons i.e. a back button and a tiny bar.
It was an entirely different experience for me. But learned to use it within few days. Now I am very comfortable with this Navigation bar. Multi-Tasking and App Switching had become faster, efficient and more productive.
But now to make it more efficient and even faster I would like to suggest to remove the back button, make the sliding of the bar to the left as the replacement of the back button. It would also improve the look of the navigation bar. I am not recommending to completely remove the back button but give us users a choice to remove it and use the sliding of bar to left as the back button.