Oh, no, very.. select few. And truth be told, they weren't.. we were not.. actual humans. [ Saber cleared her throat a bit awkwardly. It was always a bit difficult when someone assumed she was an example of the humans where she came from. No, she was a major exception.. ]

I think it would depend on the Cybertronian. For me on a motorcycle, I increased its speed and power immensely not only with my passive ability, but with my more active one called Prana Burst. And since the vehicle at that state was impossible to drive by normal means, my Riding rank allowed me to control it with ease. I believe that if I were to say.. sync with a Cybertronian like this, I would likely boost whatever aspect of them is their strongest feature. I would also focus on that aspect as well to get the most out of it. Speed and power and precision are the two things that I seem able to boost.

[ And with her passive ability, since she could read vehicles so well.. ] I wouldn't even be comfortable trying this with someone if they agreed unless I knew them quite well. I am unsure how well I'd be able to "read" them, but I wouldn't want to pry into them unless there was a total link of trust.