When they first meet Vegeta on Namek (when, in canon, they hid from him), they show themselves, fuse and
defeat him. Being not as forgiving as Goku, they kill him as well. They meet Guru faster, since they're not afraid
of being spot by Vegeta. Even after having their potential unlocked, I don't think they're so reckless as to go and
challenge Freeza; they probably wait for Goku to come. They easily defeat Ginyu Forces nonetheless.
When Goku arrives, Freeza is defeated, one way or another; even if Goku is stupid enough to let him transform,
Krihan (the fused fighter) is not. There is a chance that Zarbon (who's alive in this reality) follows them back on
Earth and becomes a Z fighter (maybe even Bulma's husband?).
Goku dies of the heart virus and Androids dominate the world. Considering Krillin and Gohan fuse to fight them,
Gohan is most likely killed along with the rest Z fighters, so Super Saiyan is never discovered. Even if Bulma goes
back in time to warn them, history just repeats itself.
If Gohan survives the initial conflict like in canon, he definitely becomes SSJ over the following years, until he gets
killed as in canon. When Bulma goes back in time to warn them, she tells them about SSJ as well, so Goku definitely
unlocks the form during the 3 year training.
Without Vegeta/Trunks, Goku is saved by Piccolo from Nineteen. Later, he trains with Gohan in ROSAT and defeats
Androids/Cell.
7 years later, Dabura is defeated.
No Golden Freeza, since Cold is alive. If Goku becomes Beeruses student anyway, he solos U6 tournament, thus
provoking Zamasu. Without Vegeta's/Trunkses help, Zero Mortal Plan succeeds.