You can write a little script for automatically starting, you won't even realise how "nvidia-settings" is opened and closed, you'll just realise your nvidia settings are set.
First, install "autostart" package via package-manager then open a console and copy these commands;
echo '#!/bin/bash' >> nvidia
echo 'nvidia-settings &' >> nvidia
echo 'sleep 2' >> nvidia
echo 'killall nvidia-settings' >> nvidia
chmod +x nvidia
mv nvidia ~/.kde/Autostart
What does these commands do?
1- Creates a bash script for starting and closing nvidia-settings
2- Makes nvidia script executable
3- Moves it to ~/.kde/Autostart