Ken body is always visible when he fight
That's not correct all, even though I don't think Ken moves as fast as Goku. Even taking aside obvious anime filler...
He's jumped faster than the human eye against the Colonel. You can see in the panel a blur and then in the next it shows he's completely disappeared, and he then reappears behind him. He did the same thing to Shin.
He also moves around too quick for Amiba to see at one point, and nearly stabs him through the head, if Amiba hadn't narrowly blocked it. He also attacks a gang of thugs so quickly that they don't even see him run by them. This is during his hunt for Jackal.
He's within Dragonball second tournament speed at times in the manga, and third tournament in the anime.
The android is on a different level and ken is on the level of goku during his fight with king picollo.
Hand to hand, Ken could defeat that Goku, though it would be a tough fight. He would OWN him when you consider Musou Tensei though, however when using energy attacks, they could kill Ken easier than his pressure points could kill Goku.
Hell goku as a child was throwing people almost out of orbit and across cities.
That didn't happen. On a physical level he has some good feats against robots and stuff, but he's never done anything like you described. Kid Goku is less powerful than Ken.
DBZ Goku punches harder than Ken, and even then, he's never punched anybody so hard that they went into orbit. That's Superman level shit.
Kenshiro, unlike Goku, most likely won't let him power up to do such an attack. One strike to the pressure points and it's all over.
The first part is true, but don't assume Kenshiro can kill them instantly. Ordinary thugs in Hokuto no Ken can be killed with a single poke in the head, but tough guys like Juuza and Fudo have resisted the effects of pressure points. I don't think Nappa would explode, so much as spray blood from his pores, ala Falco, or Raoh.