Theory Egghead is a Sabaody parallel.

Luffy, Kidd, Law,Kizaru, pacifistas all at sabaody = Egghead

Celestial dragon is at sabaody / Gorosei member at Egghead :saturn:
Bonney and strawhats is at sabaody / Bonney and strawhats at egghead

How does Sabaody end? The strawhats all vanish. = Egghead strawhats teleport or timeskip ???

Wano = Thriller Bark (Oars)

Enies Lobby = Whole cake Island (Rescue Mission)

Water 7 = Whole cake Island/Zou/Dressrosa (Luffy vs usopp, big reveal, strawhat crown)

Aokiji appears right before water 7 = aokiji appears at punkhazard
some characters reappear but the plot is completly different. older arcs that resemble egghead alot more are whisky peak (secret agents send to kill a traitor) and water7 (crime mystery)
There will be a timeskip at the end of egghead. And if you are curious what happens after the timeskip, you may read on. But do so at your own expense.

After the timeskip, luffy and his crew will meet up again at Laugh Tale.

In the final battle, the straw hats and everyone else will fight an all out battle against the red-hair pirates and the seraphim who are being lead by shanks.

Luffy against Shanks

Usopp against Yasopp

Zoro against Mihawk

Shanks never lost an arm. He is the user of the illusion-illusion fruit, that can make anyone see what he wants them to see.
He stole the fruit, he manipulated luffy into consuming the devil fruit, so that he would lead him to laugh tale island. Shanks is from the D clan and he knew luffy was joyboy from the moment he saw him thanks to his history of D and his observation haki.
To reach laugh tale, you need the blood of an innocent human. That is why Shanks needs luffy as a blood sacrifice to get his hands on the One Piece.

The D clan are the ones from the moon who betrayed their own species, the lunarians. Lead by King Joyboy. They sided with the humans to fight the lunarians. Shanks, as one of the D clan, aims for rulership of the whole Earth now.