I surrender!
It's simple really, watch Harry's magic and how he uses it, what he favors best and each time this changes it represents a significant change in the timeline. Which... generally match up to one of the mantled characters that have 'versions', GK, Odin, ect and changed after every third book, which is when the possibilities start to spin off in at least two directions each time. which if i'm right about it happening 5 times, means last one is book 17 MM...
Technically Harry 'Prime', the alternate identity and of course MM Harry's version, which twines together. the alternate spin off version is a result of time travel, multiple versions ending up in one timeline. Oh... and one where he died, always one were he failed too..
When it starts, SF, Harry is channeling lightningbolts from storms and favoring flash wind spells, in Book 2 he uses faith in magic to throw his pentacle 'like a lightning struck oak tree' at the Loup. in these books he was channeling Odin/Thor variations, In SK he changes subtly and of course, if GP had ended different his magic would have been different there but also if he'd excepted the WK mantle then.. he'd be dead, and so would that reality from Mab Nfected and Titania distraught. That's where Hwwb4's memeory of Harry being strung up actually came from, a now dead universe. second arc culminates in the Hand burning and confronting Raith(who I think in MM came out for the better vs Lara/overall) and generally focuses around if Harry picked up the coin or not.
And so forth, I don't have them all mapped out entirely, but one good clue is in Odin and Kringles descriptions, Odin is lean like a young 'runner', Harry trains running in early books to escape baddies, Kringle has muscles and Harry as the WK has been doing some serious buffing up, ect. The flying carpet in GS in Molly's mind and the one the GK rides later, the GK is the version who excelled at Mind magic mostly I think.
First Harry travels backwards in time hopping closer to his own timeline by altering events indirectly so they have the same outcome as in his(which is the one where he already went back and did all this of course) and in doing so saves himself 5 other times, making 5 universes where he ultimately succeeds... 5 times, at the same time