This will be similar on al distributions, but we’ll use Ubuntu 14.04 and Linux Mint 17 as examples here.
Yes because people need to see how to do it on Ubuntu...TWICE. What is the point of this? Mint works exactly the same as Ubuntu in doing this so all you did was explain the same way twice with a different GUI.
Everything you explained can not be translated to any other distro except Ubuntu based and inherently Debian yet you act like it is so similar.
Yes and no. That is true in some cases but it is not common. Ubuntu on the other hand uses Unity and Unity is VERY picky with what else is installed. GNOME 3 for example would probably break with Unity and KDE as well but XFCE, MATE, LXDE likely wouldn't have any issues.
It is a very cool distro to test out stuff...another great distro for that is Linux BBQ, they currently have a ISO that is setup with 76 Window Managers at once.