A lovely story! Little if any angst to it. Pretty much a feel-good story that is definitely worth re-reading.
(I might wish the author would do some editing to get rid of flow-disturbing SPAG mistakes, though, but that is neither here nor there.)
The premise that sets off the avalanche to effect a lot (but not all) canon changes is this:
One of Mrs Long's nieces falls for a rake, and the consequent repercussions of it that she must face shake the Bennet girls to the core: even Jane's rose-coloured blinders are ripped off. But the most dramatic change is in Lydia. Lydia, who is incensed on behalf of her friend Julia Long for having to bear repercussions when the lying cad is getting away with ruining her friend. She also feels guilty for having helped them get secret meetings.
What this means is that, due to the shock of this event, and with the changes in outlook on the world and behaviour Elizabeth instigates in the sisters, Lydia matures. Not unrecognisably so, no. She becomes the best version of herself. (Her fierce loyalty to and defence of her sisters and friends, her improved intelligence and perception, her refusal to come out in society at fifteen, are just heartwarming.) And the sisters' bonds with each other becomes unshakable. (Kitty and Mary bond over teaching kids at the vicarage school, for example.) So much so even Mr Bennet is shamed into taking more of an interest in his family.
This of course means that, by the time the Netherfield party arrives in Meryton well over a year later, the only Bennet to blush over still is Mrs Bennet.
But even Mrs Bennet is shown to have different facettes of her personality than just vulgar matchmaking mama. Several incidents during the course of the story (one in particular, the first one) that he witnesses make Darcy respect and admire her.
A change to canon that isn't a consequence of this eye-opening event is that in this story, Collins is a sensible and handsome man, whose patron is the Earl of Matlock, and who has previous acquaintance with Darcy. Collins also has witnessed Wickham being up to his usual disgusting self and Darcy intervening, and so knows enough to be able to not only intervene on Darcy's behalf with the Bennet after he displays his usual rudeness, but also enough to warn about Wickham.
Collins being thus changed also means something else: Jane falls for Collins instead of Bingley.
And Bingley? Has a chance encounter with Kitty at the assembly and promptly falls for *her*. And that attachment teaches him to grow a spine over the course of the story.
A detail that might be called a change to canon as well as it might be considered just showing another side of something is Caroline. She's as bad as ever in this story. Except she's also smart, and despite her ambitions and selfishness, does indeed love her brother.
I kinda adore the characterisations of everyone in this story, and the character growth they undertake throughout the story. And damn if it isn't strange to consider the friendship between Collins, Darcy, and Bingley admirable.
Everyone has their own happily ever after, even Caroline. And even the poor girl Julia Long.
(Everyone except Wickham, obviously, who gets to be of use as providing an opportunity for Bingley, Darcy, and Collins to be knights in shining armour just by being the dastardly villain he always is.)