/var/spool/pbs would be $PBS_HOME by default /opt/pbs would be $PBS_EXEC by default
You can update those variables to point it to PBS Pro OSS.
In the RSM’s cluster configuration, you should see PBS Pro in the drop-down (against the Type of Cluster).
There is ClusterJobs.py , you might need to update that file, please check 6.3.2.1. Submit Command
of the RSM User guide.