Goku goes with Krillin to Guru's house and has his potential unlocked. For plot purposes, let's say he's brought to
his 90k level. Goku keeps his PL suppressed to 5000, as in canon. Vegeta has not seen him fighting yet, so he's
tricked by the suppressed 5000 power and believes Goku is as strong as he was on Earth.
Vegeta and Zarbon fight as in canon. After killing Zarbon, Vegeta challenges Goku and soon realizes how outmatched
he is. He tells Goku that, despite having got stronger, he's still no match for Freeza. Goku does not go to challenge
Freeza, because, in canon, it seemed he was willing to listen to King Kai's and Vegeta's advice and fought Freeza
only when he had do so and after being drunken in the newfound power of an extra zenkai boost.
Gohan soon shows up with the last dragonball. Vegeta tells them he has the rest and offers them a deal: He'll
give them the rest if they use one of the wishes to make him immortal. Goku accepts, against the others' better
judgement.
The first wish is used to revive Piccolo. The second wish is used to revive Chaozu, who has already died once.
Goku knows the rest can come back with Earth's dragonballs. Knowing Goku, I don't think he'd ever break a
promise, so he's still ok with Vegeta using the third wish.
Dende refuses to grant that wish, but Vegeta cannot threaten him, since Goku is there. Goku suggests that
Vegeta chills and comes with them to Earth to begin a new life. Vegeta accepts reality and accepts, inwardly
swearing to surpass Goku someday.
When Freeza realizes he's been tricked, he goes to Earth for revenge. Vegeta has anticipated this and warned
the others, so, for one year, they've been training their asses off. For plot purposes, let's say Goku, Vegeta and
Gohan all are their post final zenkais selves on Namek.
Freeza is still in his 1st form and I don't think that even Goku will wait till he does all 3 transformations, so
Freeza is beaten easily.
Alternate Trunks shows up, reveals the Super Saiyan secret and warns them about Androids.
Early Android Saga is about the same. Cell has a much easier task, since Kamiccolo is a lot weaker (no Nail) and
probably ends up absorbed in Ginger, so everyone remains in the dark about Cell's identity.
When Androids reach Kame House, Goku does not accept to stay hidden and let his human friends risk their
lives, so he knocks Gohan unconscious and goes to stall Androids till Vegeta and Trunks come out of the spirit
room. Cell senses the battle and arrives.
By this time, Goku is beaten up and cannot do anything. Cell vs 17 goes as we know it. Without Goku knowing
teleportation, both he and Tenshinhan are killed.
Vegeta lets Cell absorb 18 as in canon. Perfect Cell announces Cell Games.
Gohan goes to train in the spirit room with Piccolo. Although he's more determined, due to his father's death,
without Goku's guidance, he cannot master SSJ. Even if he does so and somehow goes SSJ2 at Cell Games,
everything is destroyed when Cell selfdestructs.
If Cell emerges victorious and Beerus wakes up, Cell becomes his student. No FNF Saga (Cold still alive). Cell
wins U6 tournament and either causes Zamasu's jealousy (so Zero Mortal Plan succeeds) or spawns some Cell
Jrs for Zeno to play with and be distracted from erasing universes.