the whole celestial eggs gestating in planets/Galactus existing to curtail their population is from the Mutant/Earth X stories, which are non-canon and take place in an alternate universe.
however, the reason why it's mentioned here on the forums on occasion in regards to Galactus is because it's the ONLY story to date that has featured a direct confrontation between them (as even referenced in the story itself..something along the lines of "Galactus and the Celestials have never encountered each other before"
. Now granted the Galactus in that arc was actually Franklin Richards, but due to the "properties" of that reality, wherein someone merely needs to believe they are someone else and thus they effectively become that belief, for all intents and purposes Franklin was functioning as the real Galactus would.
Now, the Galactus Seed =/= one of these incubating Celestial eggs (as I understand it): whereas the Celestial eggs are just literally eggs containing "baby" celestials, the Galactus Seed, according to Odin, will yield the birth of the next universe, as well as yield the next Galactus. This was confirmed in Fantastic Four #600 (at least the part about the Seed yielding the next Galactus). FF #600 also mentioned the Seed as a "Celestial mistake" brought on by "Eternity."
NOW, these could easily be construed as metaphorical/allegorical definitions. Meaning, "Celestial" = cosmic, and "Eternity" = the length and breadth and scope of time. However, I decided to take those definitions literally (i.e., "Celestial" means the Celestials, and Eternity means the cosmic entity) based solely on the fact that solicits have confirmed Galactus and the Celestials will have a confrontation in FF 603. In FF 600, Galactus tells Reed to summon him when the earth becomes threatened. All signs point to the Celestials. And, since it was suggested in an old issue of Silver Surfer that Eternity created the Celestiails...I decided to take that literally too.
Anyway, contrary to some interpretations, this does NOT mean that Galactus himself was borne from a "Galactus Seed." His origin is the same (as implicitly confirmed in FF #600) and is more directly explained and confirmed when Galactus states the Seed is an aberration. Which means it has no precedent. Which means it is a one-time occurrence. The Seed will birth the next Galactus, but it never ever was suggested that it birthed the current one. This is confirmed once again in FF 600 (that the Seed is a once-off artifact). Who or what exactly brought on the Seed appears to involve the Celestials and/or Eternity, per my reasoning above. We'll learn more in upcoming issues.
As for Chaos King, the scan posted above contradicts Chaos War since it states the Void existed in the current universe. I.e., the universe/reality existed, and the Void was all that was present. After a time, atoms coalesced into stars and planets and the Earth came to be.
That issue of Thor Annual was published before Galactus' "true" origin was published. By that I mean Galactus' origin was initially revealed in Thor (#169, in 1969) to be an astronaut/scientist being changed/mutated into Galactus because he passed too close to "the largest sun in the universe." A completely lame origin.
This was retconned a bit in Super Villain Classics #1 (1983), which was published the year after Thor annual #10 (1982). Super Villain Classics altered Galactus' origin by stating the "largest sun" was actually the Cosmic Egg and that Taa actually existed in the previous universe, thus establishing in Marvel canon that a universe existed prior to the current one, and that Galan/Galactus came from this universe. Therefore this means that Galan pre-dates the void/nothingness mentioned in Thor annual #10.
Meanwhile, Chaos War stated that Mikaboshi pre-dated Galactus' universe.