Some changes have been made to the WC canon for this story. Here are some bigger ones, with explanation - more to come, most likely, as the story develops. A lot of changes in the story may not be mentioned here, as things may go accidentally undocumented. Feel free to ask if you have any questions about a change here or a change not listed.
Change: Spottedleaf's Heart isn't canon. Instead, Spottedleaf has been highly interested in the medicine cat role since kithood; she becomes Featherwhisker's apprentice, despite Goosefeather still being a med cat, and learns quite a bit from both cats.
Reason: I don't consider it canon in the first place, and it's extremely OOC for both Thistleclaw and Spottedleaf.
Change: Scourge doesn't exist; instead, he has become Coldfrost, a warrior of ThunderClan.
Reason: With the changes to Bluestar and Thistleclaw's personalities, the incident with Tiny and Tigerpaw would have never happened; instead, he's invited to join the clan.
Change: Swiftkit (Swiftpaw) and his brother, Lynxkit, are no longer Goldenflower's kits. They're a loner's kits, found abandoned on the territory, and foster children to Dappletail.
Reason: To introduce new blood into ThunderClan and prevent some of the incest later down the line; plus, Goldenflower getting together with both Patchpelt and Tigerclaw never really made much sense to me.
Change: Cinderpelt is now sister to Greystripe, and daughter of Willowpelt.
Reason: .. I can excuse a lot of the genetics in Warriors, but Cinderpelt, a grey cat, being born to Frostfur, a white cat, and Lionheart, a golden tabby, just doesn't make any sense.
Change: Ravenpaw, now Ravenheart, has been aged up to be the same age as Frostfur. Dustpelt was born in a later litter.
Reason: There are way too many apprentices in ThunderClan at the moment, and not enough warriors.
Change: Brokenstar/tail is now female.
Reason: Why not?