I think what you are experiencing is the icons on 2016 (even the smallest setting) are slightly larger than on 2015 therefore don't automatically show. We have lost some "real estate" for sure. You can click on the down arrows to show the remaining icons or rearrange your tool bars. A lot of complaints about this.
Edit:.. Not sure about the mouse gestures. I think I had to redo them.
All custom macro buttons on SW2015 is disappeared on SW2016