What OIDs are you using in SNMP monitoring?
If you are monitoring hrProcessorLoad, you will only see two objects, no matter what model of Palo Alto FW you are using.
It corresponds to the utilization of the data plane and the management plane.
Also, these values correspond to the values of the system resource wedge in the dashboard.
If you want to see the utilization per VCPU, you need a little trick.
Please press "1" after running "show system resources follow" to toggle view to show separate states.
I do not know the REST API that corresponds to this idea. Naturally, I don't know the corresponding SNMP objects either.
Therefore, I don't believe there is an elegant means of continuous monitoring.
In the VM-Series and PA-850, for example, the management plane and the data plane are not physically separated, and the data plane is run as a process called pan_task.
The number of pan_task processes increases or decreases according to the capacity of the Palo Alto FW and is allocated to logical cores from CPU1 onwards using CPU affinity (a feature of the Linux kernel).
I remember that the CPU utilization of the pan_task process, which can be checked with the above command, behaved a little differently depending on whether SR-IOV was enabled or not.