A/N: the Biological differences between the universe 6 and 7 Saiyans. As well as how universe 6 and 7 are much different from each other.
To start off, I'll be talking about the differences between the saiyan home worlds of the universes. Planet Vegeta and Planet Sadala.
In Universe 7, Planet Sadala was destroyed when the saiyans living on that planet in an internal conflict and discord with each other. They had to eventually move to another planet known as planet plant before overthrowing and renaming it planet vegeta. In universe 6, the saiyans clearly weren't in any conflict with each other and thus, the planet wasn't destroyed.
It would seem that the saiyans in universe 6 may have been much smarter and knew that conflict with each other would've only made things worse. And decided on no conflict with each other. But this doesn't mean they weren't fighters though. They came use their innate capacity for combat productively to fighting evil rather than causing it.
Then there's how the universe 6 saiyans and universe 7 Saiyans have advanced over the years on their respective planets. The universe 7 Saiyans had eventually been approached by frieza and his solders and agreed to work with him in exchange for things Such as armor, advanced technology and other things. Frost did the same with the but lied to the saiyans about fighting in wars since frost was the one staring wars in the first place. But the universe 6 saiyans had things such as old classic style houses where as the universe 7 Saiyans had ones similar to frieza buildings.
Next, there's the saiyans personalities. The universe 7 saiyans were brutal and violent and basically lacked compassion for others except themselves. The universe 6 saiyans were different, they were fighters, but not ones who do evil deeds like the universe 7 Saiyans did. But there are some saiyans who were still roudy and all that. As seen with the gang of saiyans that work for caulifla.(At least I think they work for her or they're just terrified of her).
But none the less, the universe 6 saiyans are more intelligent. I'm some ways I think. We don't know all that much about planet sadala.
And finally on to how they transform. The one thing I need to bring to the table would haft to be the S-Cells.
(this is just an example picture on how they have the potential to transform and possibly gain new and different forms).
The S-Cells are microscopic cells found in most Saiyans. The amount of S-Cells would haft to depend on the spirit of the Saiyan. Like, the more gentle the spirit, the greater the amount of S-Cells. Or alternatively, when a Saiyan would increase their battle power, it could also increase the amount of S-Cells in their body. S-Cells are essential to becoming a Super Saiyan, and when a Saiyan has gained enough they can transform by feeling intense levels of anger or sadness. Or alternatively, by focusing their power into a tingling sensation in their upper-back, the Saiyan can trigger the transformation into a Super Saiyan without the need for emotional stress.
That's why saiyan like cabba, kale and caulifla were able to transform faster than Goku, vegeta and Gohan could. Goku and the others didn't know that and went through the phase of emotions instead where they faced many things that lead to their transformations. And they have more potential to train and transform to even further forms. While they may not get god forms since Vados has a somewhat different personality than whis, they'll still get strong forms that could be as strong as, if not stronger than god forms.......maybe any. Also, Even though that the universe 6 saiyans turned super saiyan, it's not exactly the same as the universe 7 one. I mean that it a way that it's still super saiyan, but in a way that it's still a new and unique thing.
One more thing, kale's berserker form is not legendary super saiyan. It may look like it. But it is not it. It's kinda like ultra super saiyan. It looks like the legendary super saiyan form with some similar features. But it could still be something different.
(If perhaps Toriyama could just give a name already).
But that's all i got. If sees something I've missed or wants to add more to the info. Just leave in the Comments.