In the exported CSV parameter data of the energy meter, what does the Voltage (V), Current (A) and Power (W) parameters represent? Are they the peak or average values of those parameters over the 5 minute interval of interest?

Hi:
There is no extra logic in these readings,all parameters (current,voltage,active power and kWh) are just the real reading at that sample points.

By default, the power meter sample each 6 seconds and upload to IAMMETER every 1 min(6 samples will be one cycle, the sixth sample result would be uploaded to the IAMMETER).

This is an article that introduces this 

https://www.iammeter.com/newsshow/Blog-time-interval-parameter