Turn off animated mouseover effects:

In KDE, go to the main Application Launcher button –> Control Center –> Desktop –> Panels (or open "kcontrol" from an xterm)

Click the Appearance tab

Uncheck "Enable icon mouseover effects"

Turn off GUI effects:

In KDE, go to the main Application Launcher button –> Control Center –> Appearance & Themes –> Style

Click the Effects tab

Uncheck "Enable GUI effects"

You may need to log out and log back in to activate the changes.