For switching between monitor and tv I use display rather than nvidia-settings.
I noticed nvidia-settings didn't always retain the settings I had set.
No issue using display in cinnamon system settings.
Dual output issue
On reboot disable output to TV via hdmi was enabled again after being disabled a work-a-round is to:
create the following folder
sudo mkdir /usr/share/gnome-shell/modes
this seems to resolve the issue