My experience applies to my own part of the world, the Pacific Northwest (specifically Vancouver Island, Canada).
I've spent a few unplanned nights out and two planned nights to discover what works. (More nights planned)
I've come to the conclusion that so far, for my region, one of those small disposable ponchos and a half dozen pocket warmers will keep me alive. The poncho serves as a mini-tent that I can squat under. Rain clothes don't function well when you're not vertical.
Fire is over-rated. In most cases it's emotional comfort and something to do. The warmth of a small open fire doesn't penetrate well-insulated clothing, and sparks will destroy artificial fabrics.
In bug season I consider a net essential. Running around in the dark to escape the torture would be dangerous.
A powerful mini flashlight with strobe would probably repel a cougar.
It will take many more trial nights to really learn what works. I suggest that anyone who packs an emergency overnight kit should test it out under real conditions in all weather, with the safety of the vehicle nearby.