Can I use both PolicyPakOn Premise mode and PolicyPak Cloud simultaneously? Do they clash?

Netwrix PolicyPak On-Prem Suite and PolicyPak Cloud have been designed to play nicely together.

Therefore, you can use either the PolicyPak Cloud to deliver your setting and/or, say, Group Policy or SCCM to deliver your setting.

All policies are simply merged together. If there's a conflict, the on-premise directive (say, using Group Policy) wins.