Again, I still think you are over thinking this, and ascribing too much of what you see in a pro-peloton to your local rides.
IME, most group rides work one of three ways:
1. Straight double file.
2. Rotating paceline on the front - maybe double paceline on the back for those not interested in rotating
3. Mass going down the street - sometimes two wide, sometimes more - these tend to be the real race-like hammer rides.
I have not seen a group ride do any actual echeloning since I was in Texas, where we had zero trees and a 15 mph wind was the base standard. It wasn't considered windy until we got to 25-30 mph winds. (These are not East Coast Watts exaggerations. We road through wind farms.)