I want to SSH into the Pi to change all the settings without a GUI interface.
Modify the config file of your interest in the /etc/rds/ folder and then restart the Raspberry Digital Signage service: systemctl restart rds.
For the network, standard /etc/network/interfaces.d/* and /etc/resolv.conf files are used.
For the locale and keyboard, the standard system files /etc/default/locale and /etc/default/keyboard are used.
For the rotation, the /boot/config.txt file is used by the Raspberry Digital Signage stack.