It's a very complicated subject Doonhamer as each individual has a different reaction to the various chemical constituents of a given drink.
I don't actually know of any conclusive scientific research on the subject, which is odd given how widespread a problem it is.
But at the risk of going over what you already know the main factors are Dehydration and Electrolyte Imbalance which obviously results from increased urine production that causes most of the more common hangover symptoms such as thirst, general physical lethargy, dryness of the mucous membranes, dizziness, and feeling lightheaded. Add to this perspiration, sickness, and diarrhea and the body can lose additional fluids and electrolytes which makes it a whole lot worse as alcohol inflames the stomach and intestine. Alcohol can also lead to liver damage (with associated symptoms) gastric acid along with pancreatic and intestinal secretions that result in abdominal pain and sickness. Then you might well suffer from low blood sugar as the bodies glucose production is debilitated and as glucose is the main energy source for the brain this can lead to tiredness, general weakness and a bloody temper. Also sleep is usually disturbed and shortened and of a poorer quality than usual.
Also because alcohol is in effect a toxin it can result in a widening of blood vessels that can cause headaches.
And then withdrawal as heavy drinking can suppress the nervous system so when you go 'on the wagon' it can become unbalanced and hyperactive state which causes the tremors and rapid heartbeat know as the DT's
Quite why one person can drink a whole bottle of Jack Daniels and still function, seemingly, quite normally the next day and yet be laid low by a couple of pints of Cider... I have no idea, sorry.