Second, you will reduce the uptime and stability of your relay, thus it will lose consensus weight if you reboot the machine once a day.
Unattended-Upgrade::Automatic-Reboot "true";
Does not reboot your machine "once a day", it reboots when a new kernel requires a reboot. Which on Debian stable / Ubuntu LTS is far from being a daily event. And the frequency of reboots actually should not differ compared to manual reboots.