Hide KMix Applet
Create the file .config/autostart/kmix_autostart.desktop
[Desktop Entry]
Hidden=true
Hide Printer Applet
Create the file ~/.config/autostart/printer-applet.desktop
[Desktop Entry]
Hidden=true
I learned a new form to hide an autostart program :P thanks for your question!!!
For any program autostarted in /usr/share/autostart create a file with the same name in your ~/.config/autostart with that content. It will start hidden.
Disable autostart of KMix & Printer Applet
Delete the autostart files as root (backup them first if needed)
/usr/share/autostart/kmix_autostart.desktop
/usr/share/autostart/printer-applet.desktop
Maybe, if you update the kde desktop they will be created again. Create a empty file in its place.
Remove completely KMix
yum remove kdemultimedia-kmix kdeutils-printer-applet
In my system I can remove the two package without having to remove anyother.