So whether they complaining insomniacs don't feel good and thus complain, or complain and thus don't feel good, we at least know that it's not the sleeplessness (as it is common to both groups).
I am a night owl and so find a shitty nights sleep will result in a shitty morning; but I’ll feel much better by the end of the day. Whereas a morning person might wake up without issues and only pay the price later on (and counter with an early night).
Not according to all medical advise I've read (no lifestyle advice / lifehacks).
The body really needs its sleep, and the amount is more or less fixed to 7-8 hours.
There's only a small (1-2 hours variation with age, not with individual people).
From everything I've read (at the medical documents/research, not the lifehack level) it doesn't vary much. It varies only a little with age and the presence (or not) of a gene, but it's the same across such groups (e.g. not some individual organism preference).
Those that sleep less simply damage their body, and will pay for it later and with reduced functioning (compared to enough sleep) -- it's not that they actually "need less". Same for those that sleep more.
https://www.ncbi.nlm.nih.gov/pubmed/12683469
https://www.ncbi.nlm.nih.gov/pubmed/12603781
Most researchers now believe that the relationship between sleep duration and mortality (link is external) is best described as a U-shaped curve with the right side of the “U” considerably higher. That is, less than 5 1/2 hours of sleep is associated with some degree of increased mortality. However, sleeping beyond 9 or 10 hours per night, is associated with a markedly increased mortality