OpenPlant Power P&ID Projects Definition
This configuration is for Ss3, Ss4, and Ss5. This is showing the Ss5 paths. Substitute PowerPID (SELECTseries 3)\ for PowerPID (SELECTseries 5)\ for Ss3. Substitute PowerPID (SELECTseries 4)\ for PowerPID (SELECTseries 5)\ for Ss4.
There are two types of Projects: Workspace and Database. This explains the differences.
C:\ProgramData\Bentley\PowerPID (SELECTseries 5)\WorkSpace\Projects
The Workspace is required here as well but that the Database Repository is an added feature when using the Bentley Plant framework.
OpenPlant Power P&ID Schema locations
This configuration is for Ss3, Ss4, and Ss5. This is showing the Ss5 paths. Substitute PowerPID (SELECTseries 3)\ for PowerPID (SELECTseries 5)\ for Ss3. Substitute PowerPID (SELECTseries 4)\ for PowerPID (SELECTseries 5)\ for Ss4. Note for Ss3 and Ss4, the schem file versions will be smaller, ex. Ss4 has bmf.01.02.ecschema.xml.
Part7.01.00.ecschema.xml
Also see Schema Hierarchy and Assembly Locations