Removing XFCE after installing KDE OR keeping them both

I just installed the KDE DE following the official instructions “Install Desktop Environments”.
The final step was:

Create a new user for the new desktop environment
sudo useradd -mG lp,network,power,sys,wheel <username>
sudo passwd <username>

which I thought that would mean that I could have a user using XFCE and a second user using KDE. However, in the end both users use the KDE DE, without me having removed XFCE.

So I have 2 questions:

  1. Is it possible somehow to switch the DE of my first user back to XFCE?

  2. If not, how can I completely remove XFCE so that it doesn’t use disc space?

Technically all users have access to all DEs installed. The creation of a second user is recommended in order to avoid mixing graphical configurations.

You should be able to just select XFCE in your display manager.