The Google Cloudprint information in previous guides is helpful. The daemonizing of the service worked with systemd but not as well as one would expect. I may have found a solution.
FYI the lastest armooo/cloudprint has been updated to address Oauth2, and the service works (Pogoplug E02) with the main process, not daemonized. For example,
[Unit]
Description=Startup Google CloudPrint
Requires=org.cups.cupsd.service
After=org.cups.cupsd.service network.target
[Service]
#Type=oneshot
#PIDFile=/var/run/cloudprint.pid
#ExecStart=/usr/bin/cloudprint -d -p /var/run/cloudprint.pid
#ExecStop=/bin/kill -TERM $MAINPID
#RemainAfterExit=yes
ExecStart=/usr/bin/cloudprint -p /var/run/cloudprint.pid
[Install]
WantedBy=multi-user.target