Explanation
To override a device and network setting applied by a template, you can either configure the setting locally on the firewall or override the setting on the template stack. Configuring the setting locally on the firewall will copy the setting to the local configuration of the device and will no longer be controlled by the template.
Overriding the setting on the template stack will apply the setting to all the firewalls that are assigned to the template stack, unless the setting is also overridden locally on a firewall. Changing the setting on the global template will affect all the firewalls that inherit the setting from the template, which is not desirable in this scenario. Configuring a service route for DNS on a different interface will not change the DNS server address, but only the interface that the firewall uses to reach the DNS server. References:
Override a Template Setting
How to override panorama pushed template configuration on the local firewall Overriding Panorama Template settings