Darren is right that we used globals and locals following our own best practices, so there is no need to be concerned about this (globals are used primarily for configuration). However, I would strongly advise not starting from a Sample Project for the CLED exam. I would recommend referring to the CompactRIO Sample Projects to gain an understanding of the general software architecture that NI recommends for embedded control & monitoring applications, as your design should resemble this architecture to some extent (your design will need to accomplish similar tasks). However, the architecture you implement within the exam should be a scaled back, much less complex version. We've noticed that those who have passed this exam, were more efficient building their own architecture from scratch, and using basic LabVIEW primitives (Queues, etc.) over more complex APIs like the Queued Message Handler API that ships in the Sample Projects.
I hope this helps - please let me know if you have any other questions or concerns!
Meghan