I have a few questions about stats. What do they mean? What are the differences between Supercoach/Fantasy/Champion Data etc? Where to go to find them?

As best I can tell, the most authoritative stats are from Champion Data. Is that right? Are they publicly available? Either for AFL or NEAFL? On the one hand I think you pay to have access to them. On the other, I think the AFL do pay to have that access - so do they make them available? However, I have heard that clubs don't necessarily use Champion Data. If not, what are the good alternatives?

Player ratings, especially on afl.com.au, often seem to be based on 'AFL Fantasy' points, whatever these are. I have read that these are "similar" to "DFS" stats which, in turn, are quite an unsophisticated system. Whereas Supercoach, apparently, is closer to Champion Data and is more sophisticated. Given Fantasy ratings are so unsophisticated why are these published by afl.com.au when they clearly have access to Champion Data which is so much preferable?

What are the best places that I can go to find stats either about a player in a given competition (e.g. AFL, NEAFL) either historically or to get a (relatively) sophisticated evaluation of a player's game? Is Supercoach the most sophisticated publicly and freely available? Is it publicly and freely available at all? If so, where?

Grateful for all explanations and info.