For what it's worth (not much)
My version of Greyhawk is a combination of the 1983 boxed set, the Living Greyhawk Gazeteer, alterations of the above, plus the SCAP adventure path, and results of actual play. Though the details will vary, I suspect a lot of people have customized Greyhawks like this.
In actual play, it's nearly all been in Bissel and Cauldron (the city in SCAP).
The easiest way to explain the overall combination is: it's LGG, but the Greyhawk Wars never happened as such. Instead:
1) The Great Kingdom collapsed in a massive civil war. It's just like LGG in results, but with less glam metal outer planar help in getting there, and more war, famine, and pestilence. Almor and Medegia were destroyed, and Nyrond was pulled in and weakened. Rel Astra, the North Province, and Ahlissa vie for power in a loose, exhausted peace.
2) Furyondy is at war with Iuz. Iuz conquered the Horned Society, the Bandit Kingdoms, and the Shield Lands, and menaces the Vesve, the Wolf Nomads, and the Barrens.
3) Unrelated to Iuz, Stonefist (not "Stonehold") has invade Tenh, and Nyrond is on its knees from fighting in the Great Kingdom, plus the threats from Iuz and Stonefist. Again, it looks like LGG, but got there will less glam metal.
4) Unrelated to Iuz or the Fall of the Great Kingdom, Lolth and the giants invade Sterich and Geoff. Due to successful adventuring by PC's (in G123Q1), these lands fought off the giants & drow, and are basically fine.
5) In secret alliance with Iuz, but for it's own reason partially triggered by PC's in the Lost Caverns of Tsojcanth, Ket has invaded Bissel. With its large standing army (there in 1983, missed in Greyhawk Wars it would seem), the help of the Velunese cavalry, and the help of Gran March Brotherhood of the Sword (who aren't need in Sterich and Geoff, thanks to the PC's), Bissel has recovered from early losses and is now in the ascendent.
6) A gate from the Yatil Mountains to Cauldron was just discovered by yet another party of PCs, in the Forge of Fury, connecting to the Malachite Fortress (in SCAP's Life's Bazaar). Only the PC's and the duergar now about it so far. The duergar are fighting for their lives against the White Kingdom (Kingdom of the Ghouls), with the Kuo-Toans and Mind Flayers as loose allies. The Drow are neutral and less important right now in the Underdark, what with the death of Lolth (thanks to PCs') and the destruction of their big attempt to invade the surface world. Cauldron and Sasserine were colonies of the Hold of Sea Princes, which has been conquered by the Scarlet Brotherhood (unrelated to the other conflicts).
7) There are other dark forces at work, besides Iuz and the Kettites and the Scarlet Brotherhood. PC's need to figure out who and why, but it's been set in motion by the above big issues in "latter day" Greyhawk. "Wheels within wheels", as Nitescreed used to say.