A 2nd row increases the size (height) of the taskbar. I really don't like to scroll to get to buttons on the taskbar. You have to position the mouse pointer just right.
This new overflow menu is really slick. You just click on the 3 dots (aka ellipsis) at the right end of the 1st row and up pops the additional overflow buttons. Click on the 3 dots again and it disappears. I used to limit the number of buttons on my taskbar to 1 row because I hated to scroll. Now I can have as many buttons as I want in the taskbar and now the buttons in the overflow menu are so easy to get to. I just love it when I get things to work the way I want when it allows me to be more productive.
Thanks!