I know how to change the appearance and size of the launcher icons via GUI; however, in 14.04LTS I used
dconf write /org/compiz/profiles/unity/plugins/unityshell/icon-size 18
To adjust the size and it worked via command line. My problem is that doesn't seem to work in 16.04 because dconf tools aren't installed.
I would like to use the native gsettings and change it that way. I found this for the launcher move from left to bottom
gsettings set com.canonical.Unity.Launcher launcher-position Bottom.
But I can't find anything to adjust the icon size