As both Plant and P&ID include a default "Imperial.cfg" file and knowing that CADWorx P&ID application limitation of using the "Imperial.cfg" for inch-based projects so named, has anyone used a single.CFG file for more than one CADWorx application?

Currently, I support one plant only. Using a single .CFG seems a good fit.

Does this make sense: Why or why not?

I have done it before without issues, although if you are using PIDVIEW to link the PID and the 3D model, you could have seperate projects and DB's

I actually prefer this method.

In the past, only ever used one cfg per project, this would be for P&ID and Plant, though were not using any databases. For demos now, I use one cfg for P&ID, Plant, and Structure. Neither ever posed a problem, copied the OotB cfg, renamed, and used from there.