Couple of Answers Needed

[MitchM]

These topics have been discussed and researched in the past .
How far a person wants to get into the details is up to the individual.

Salinity, lighting, water flow, nutrient levels can vary quite a bit in nature which can lead to corals that are able to survive larger swings in the various parameters.
When we keep the range of our tank environments in tight parameters, our corals are more susceptible to small changes in those parameters.