I just finished the book, so I can respond to this now:
I also just want to ask whether Allegience in Exile fits more into George's Crucible world than into the more mainstream novelverse (a la Vanguard and Forgotten History)?
I'd say it's ambiguous. Some of its details, at least in the brief final chapter, are a little inconsistent with Crucible
's version of the end of the 5YM, but not so much that they can't be reconciled if you squint a little. Ditto with the main novelverse -- it makes some assumptions that don't mesh perfectly with the Ex Machina/Forgotten History
version of events, but the differences are pretty much matters of nuance, so they can be made to fit easily enough. I'm not sure it entirely meshes with The Rings of Time
, though, since they both span a fair amount of the last few months of the 5YM and it might be tricky to fit them both into the available time. But at worst you'd only have to fudge a couple of small details to reconcile them. There are already greater continuity glitches in the novelverse, not to mention in canon itself. Heck, if you wanted, you could even reconcile AiE with the Mission's End
comic without much fudging, or with DC's "Final Mission" annual. (It doesn't quite fit with the others. In The Lost Years
and the '95 DC version, Kirk has no advance intimations of his promotion, and the SNW10 story puts the end of the 5YM right after "Turnabout Intruder," disregarding TAS.)
Although, given the reference to the bit of novelverse continuity discussed in spoilers above, I imagine that would give the edge to the novelverse as the most likely "home" continuity for the book.