Answer:

 Depends on your contract and workflow.

If you have access to using AutoPIPE Advance or AutoPIPE Nuclear version and would like to create a Stress Isometric, than Yes, download and install "OpenPlant Isometric Manager" and any prerequisites required. Again, remember that OPIM is a separate download and needs to be installed separately from AutoPIPE. 

If you only have access to using AutoPIPE Standard edition, than No, do not download "OpenPlant Isometric Manager"

See Also

Will I incur additional cost/usage when using OPIM?

Can a Stress Isometric be created without an additional OPIM license?

"Bentley OpenPLANT Isometrics Manager not found"... message appears when configuring AutoPIPE Licens

Stress Isometrics - AutoPIPE

How do I download, install, and license AutoPIPE?

Bentley AutoPIPE