One of the greatest appeals of Greyhawk, and one that Gygax himself pointed out in the 1E Dungeon Master's Guide, was that a lot of the setting's details were left deliberately sketchy so individual groups could put their own spins on it. You could make the world dark and bloody, more light-hearted and humorous, high or low magic, pulp Conan-style adventures or epic Tolkienesque battles of good and evil, whatever suits you.
This was also elaborated in how the setting was developed through modules as opposed to the sourcebook/novel-heavy approaches of Dragonlance or Forgotten Realms. There were few arbitrary additions to official canon outside of the modules themselves, and your gaming group directly influenced how they turned out. If the drow were defeated in the Against the Giants modules, for instance, then Geoff, Sterich and the Yeomanry will not be invaded and you've just radically altered a possible outcome of the Greyhawk Wars. Potentially dramatic shifts in play could be worked out by your group based on your own actions, rather than on pre-set outcomes decided on by sourcebook and novel authors.
Hence why so many fans hated the Greyhawk Wars, and I also have a certain distaste for Living Greyhawk-from From the Ashes onwards, official setting canon was now being added by TSR/WoTC fiat that many players had no say or influence over, something that to my mind goes directly against the original spirit of the setting. The one golden rule of Greyhawk is, to me, that your group alone decides what is canon. The 1983 boxed set will be an obvious jumping-off point, but from there you should feel free to take what canon you like and discard the rest, an approach I use in my own Canonfire articles, where I only do research if I feel like it and include only those canonical facts that I like.
Don't put too much faith in Nitescreed's Grey in the Hawk, as it's largely a series of strawman attacks directed against the Forgotten Realms. That said, both that essay and some of the other posts here demonstrate the conventions that developed among devoted fans-namely, that the world is a firmer shade of neutal grey rather than a battle of good versus evil; that magic is not as prevalent as in a place like the Forgotten Realms; that it's more Robert E. Howard and Fritz Leiber than J.R.R. Tolkien in its overall tone, although there's plenty to work with if you decide to go the Tolkien route; that the forces of good and evil are somewhat more pragmatic in that good nations can be at each others' throats or can ally with ostensible enemies if they work towards a common goal; and that the overall power levels are lower than they are in FR, for instance.
These tropes are generally accepted by Greyhawk fans, although you can and should ignore any or all of them if you think it would benefit your campaign. Greyhawk is flexible enough that you can alter the tone and power level as you see fit and still run an enjoyable game.
Again, if there's something in canon you don't like, throw it out and make up whatever you want in its place. I personally prefer to assume that Expedition to the Barrier Peaks never happened, that there are no crashed starships, robots or other science fiction knicknacks in the setting, to the point where gunpowder and the internal combustion engine do not function, which precludes the rise of guns or industrialization and keeps Greyhawk more or less permanently frozen at its pseudo-medieval technological level, although gnomes can elaborate other forms of technology, like combination locks and printing presses.
Does that have any basis in Greyhawk? Not particularly, since Gygax's and Kuntz's original games were littered with sci-fi tropes, but I prefer to keep Greyhawk pure and untouched by these things, and the setting is flexible enough that I can quietly put them in the dustbin without too much fuss.