Based on those spoilers, the story mostly takes place in "the 36th world". The world has been looping because of Pucchi's Made in Heaven, and a handful of people have survived each look, ending up back in their time afterwards like Emporio was at the end of Part 6. The 36th cycle is important because it fulfills one of Dio's prophecies and it allows Cars to sorta come back from his state of not thinking because all 36 of them land on Mars (Cars is immortal so he survives the looping reality).

As for like, the entire rest of the story, how these things connect, or where it ends up, you'd have to read it. Like I said, I'm reading it but I'm also reading a ton of other books and this one is particularly long. The beginning is about Jorge Joestar and Lisa Lisa as kids. Jorge is a little crybaby type kid who gets bullied, and Lisa Lisa stands up fro him. But then Straizzo takes Lisa Lisa and moves away. Then Jorge goes to school alone and the guy who was bullying him is dead. That's all that happened in the first chapter I read. According to those spoilers, the whole "36 Cars'" thing happens somewhere in the middle. It's a spoiler, it's the answer to a mystery posed earlier in the book that probably explains a lot of stuff.

he Japanese Jorge World is Earth after 36 cycles.

This is a fact established in the middle of the story when they run into all of the Cars' assembled on Mars.

Originally when I heard there was a character with the same first and last name as "George Joestar", I assumed it was the a "SBR and Jojolion-type parallel universe setup". But I didn't know it had repeated 36+1 times. The number 36 is taken from the "36 souls" from the "Way to Go to Heaven" that Dio left behind. The 36 souls are explained as "The 36 bodies of Cars that accumulated after the universe repeated 36 times."

The distortion in the Japanese Jorge's world is the result of the effects of the "strain" from the universe repeating. Perhaps the fact that only Japan is left pretty much unchanged is the effect of a singularity existing there?

Cars coming back to Earth.
Cars is a really nice guy.
The Holy Corpse from SBR is Dio.
The Dio in Part 3 is fake. The real Dio is still alive. OVER HEAVEN was written by fake Dio.
Dio's 14 words on how to get to Heaven are revealed.
Morioh gets separated from Japan and grows legs and starts walking around. This has to do with one of the words.
The island the Passione family is on starts moving and collides with the Morioh island.
Like in SBR, the characters in this world are slightly different, though many have the same names.
All stands are different except for Heaven's Door, Gold Experience (Requiem), and Killer Queen. The rest are similar but different. Narancia's stand is "U Boat" and is a deep-sea diving Stand, but still has rapid-fire weapons and is remote controlled.
Giorno has already taken over the Passione Family.
Doppio exists independantly of Diavolo. His Stand turns objects into telephones.
The one who shares a personality with Diavolo is Giorno.
The reason the same people and Stands exist are because they survived a loop into the next repetition of the universe, like Emporio.
Giorno used GER to "nullify his death" and move through space time, when time sped up at the end of part 6. Rohan just kept working on his manga and turned out okay.
Kira seems to be connected to the Deadman's Questions story. He's more nonchalant now.
Diavolo used Crimson King to not truly die, but only the version connected with Doppio died.
Jorge is not killed by a zombie.
Cars "remembers" about Stands.
Ultimate Cars and Ultimate Dio team up.
Jonathan comes back to life. Because Elina was storing his head. He fuses with the holy corpse and becomes Ultimate Jonathan in the SBR world. So the corpse is Dio+Jonathan. This is differenty from Johnny.
Kira uses Bits the Dust to go back and time and do stuff.
Because... Cars takes over Killer Queen he enduces explosions to run time backwards until it's back to only "one time the universe has repeated" which is the SBR world That's how Jorge and Jonathan end up in the SBR world.
The reason Cars does things is because he hold something close to "respect" for human bravery and ambition.
Killer Queen stops obeying Kira and follows Cars.