First, I'm in the same boat as you are, and here are few of my insights:
You are trying to create a test sequencer - There are off the shelf products that do that (Teststand is NI's solution - $$$). For architecture, anything from the basic QMH to a full blown actor framework with asynchronous actors can be used - in my case, I have used QMH with few extra threads for safety, logging and report generation.
OOP is a way for the designers to think about software modules and abstraction. Do you need such things? Are you planning on supporting multiple models of PSU, loads and other test instruments? If so, OOP provides a convenient way to create those abstraction layers. If you decide on using classes, you should avoid using PPL, they break each other in weird and wonderful ways.
For data logging, I suggest both a central parametric database and local Excel or Calc reports.
Test templates and deployment: You should consider creating a standardized test template project, along with build specifications, so your operators will use an executable and not the full LV IDE.