Cinnamon HiDPI & multi-monitor: need help

I've been using a multi-monitor setup for ~2 years with nvidia-settings, but that somehow broke with a recent update so I've been scrambling... Quite the headache...

The main issue I have is that somehow /usr/lib/cinnamon-settings-daemon/csd-xrandr does not auto-start when I log in. I have a correct $HOME/.config/cinnamon-monitors.xml and when I manually run csd-xrandr after logging in it does exactly the right thing. I do have /etc/xdg/autostart/cinnamon-settings-daemon-xrandr.desktop and the other daemons in that dir do get started, but I can't find anything about xrandr in any log file. How do I troubleshoot this?

Another issue I have is that the login screen doesn't do the right thing. Where is the equivalent of cinnamon-monitors.xml for the login screen?

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