I hate missing all this WAR OF KINGS discussion, since that means trying to comment to a few points raised at once and that makes a post long.
Right now I agree with the sentiment that WAR OF KINGS is closer to ANNIHILATION than CONQUEST was. There is more planet-bursting action right from the bat, and the centers of the narrative focus have more charisma. The Inhumans and the Starjammers, specifically Havok and Polaris, have more charisma than Adam Warlock and Phyla Vell did in CONQUEST, which was a bit of why it wasn't as strong as ANNIHILATION; Abnett & Lanning picked the wrong stars. As supporting members of a large team on GOTG who get maybe 1-2 issues to themselves out of maybe 7-8, Warlock and Phyla are fine. They just can't carry an entire event. The Inhumans and some spare X-Men, however, are better suited for the role.
Personally, I think putting more elements into "Cosmic Marvel" this year and the end of last was a good idea. The Shi'ar may spend much of their time in the X-Men wheelhouse, but they also are a major space power and among the last left after Annihilus and Ultron ravaged other empires, such as the Skrulls and the Kree. They even ruled over both at one time. Not having the Starjammer/Emperor Vulcan stuff interact with the rest of the space line felt artificial, and I am glad that has ended. I didn't read Brubaker's RISE AND FALL OF THE SHI'AR EMPIRE nor did I read the EMPEROR VULCAN mini. I basically had WAR OF KINGS SAGA, then KINGBREAKER, and the event proper, and I'm fine. Granted, I also read DEADLY GENESIS that created Vulcan, but that isn't good at all. Vulcan works far better as an insane cosmic tyrant than trying to make a big deal about his X-Men roots, because deep down he isn't much of a character. One doesn't need to be a deep character to provide a good space menace for a cosmic crossover.
I also think this is Havok's big moment to finally step out of Cyclops' shadow and take down a big bad. Once upon a time Cyclops had plenty of big moments wasting Apocalypse in X-Factor or Mr. Sinister in Inferno. Havok really hasn't had a big enemy to his own until now, and honestly I hope he isn't denied that moment of victory over Vulcan just to make up for Black Bolt seemingly getting his ass kicked by Hulk or something (even if it was a Skrull). Right now I want to see Bolt avenge himself over Gladiator.
As for the side-titles, I am curious how they fit in as well. NOVA's place is obvious; the corrupted-by-power Worldmind is about to lead his new squad of novice (and mostly Earthling) Centurians right into the "War of Kings" in response to those Kree worlds being destroyed by Nega-Bombs, and likely Richard Rider's fears will come true. The new Corps are in no way ready, and will be slaughtered en masse. That brings him into it easily.
As for GUARDIANS OF THE GALAXY, I don't know what brings them into it, especially as their own title has their own worries. There is Blastaar wanting to invade Earth via the 42 prison in the Negative Zone, which he was set up to rule by Ronan before the Inhumans came in to fill the power void left by Annihilus' death (his minion's forces, led by Ravenous, suffered losses via Phalanx attacks in CONQUEST). The Universal Church of Truth is likely protecting a cocoon that has Adam Warlock's evil entity, Magus, which is due for his decade resurrection (least that is my guess). Possibly it is due to Phyla Vell becoming a new avatar of death for Oblivion, as the WAR OF KINGS will likely provide a lot of souls to collect. Still, the GOTG are out to protect the universe from destruction since the last space wars have weakened space & time; a third war between the Shi'ar and the Kree/Inhumans/Starjammers would certainly merit being involved.
The only real mystery right now is Darkhawk. WAR OF KINGS: DARKHAWK basically claimed that instead of being created by an alien criminal and his band of scientists seeking ultimate weapons, Chris Powell is in fact one of two "Raptors" left in the universe and they are basically a band of space cops. That's a bit cliche and leaves a lot of things to be explained; Darkhawk's 90's series lasted 50 issues and covered his origins for a lot of it. The Nova Corps are basically space cops, so it seems pretty stuck. "Oh, Darkhawk is a space cop too, just, uh, from a different race. Yeah." That's like having the Green Lantern Corps have competition from non-GL's.
I am curious how the event will work overall considering Abnett & Lanning are writing ALL of it; the core mini itself, Darkhawk's side ASCENSION mini, and the two ongoing titles that tie in, NOVA and GUARDIANS OF THE GALAXY. If it succeeds or fails, there will be no other writers to credit. Will it all read like a long story, or will the core story be in WAR OF KINGS, with details being in the side books? That was how CONQUEST worked, with all of the elements coming in for the finale (Nova was really not involved in the core CONQUEST mini until the last issue when he and Warlock from NEW MUTANTS joined the fight against Ultron).
Even with these concerns, Abnett & Lanning have impressed me on their tenure on NOVA and GOTG, and with a better cast of stars heading WAR OF KINGS, I think this will be an improvement over their last event; they've had a year to hone their craft, after all. I have more faith in this being at least decent than I do of whatever DARK REIGN crap is due in the pipeline from Bendis.
Having the Inhumans rule the Kree, who created them, is a nice touch, and I am liking their new sonic based technology (makes sense since Black Bolt is essentially a sonic powered demigod).