The workload of the PLC is mainly represented by the cycle time of the tasks. Please have a look to the online documentation"ctrlX PLC Engineering, PLC programming system, Application Manual" chapter "ctrlX PLC Engineering System -> Application at Runtime -> Monitoring Tasks" to see how to check them.
In ctrlX PLC 01V08 the PLC tasks are running on CPU core #02. It is recommended to keep the CPU load generated by the PLC below 70% on this CPU core, because other processes (e.g. communication) are using CPU core #02 as well.
For example: If you have a 2 msec cyclic PLC task, the execution time of this task should not exceeed 1,4 msec.
With ctrlX PLC 01V10 a variant of the PLC App will be available which allows multi CPU core usage.