Out of curiosity, which one created Peter's personality and situation: Teenager with dead parents, high school loser, ect.

Similarly was it Lee or Kirby that came up with the FFs personnas? The Big Brain, the gruff tough guy, the young daredevil and uh a girl. Kirby had been working with those archtypes forever in works like the Newsboy Legion and Challengers of the Unknown.

In the case of FF #1 Stan's synopsis does survive, but even in that case we don't know what Kirby contributed, because he and Stan almost certainly discussed the plot and characters before Stan typed the synopsis (that was the way they almost always worked).  As you pointed out, the characters are pretty standard Kirby archetypes, and it's well-known that Kirby based Ben's personality on himself.   

What's interesting in that first synopsis, wasn't  Ben's personality originally going to be much more sinister...almost like a "Dr. Smith" type villain from within. Granted it's been a while since I read it, so I might be misremembering.

Don - Such is the story when you do a work for hire - you don't have any control over the toys when someone else starts playing with them (unless you're Stan and you're also the editor).