Concerning Scotty's alleged estimate padding:
In TOS, I don't believe there was ever any indication of such. In fact, there was never any indication at all that Scotty and Kirk were not always communicating with great efficiency and clarity and were always on the same page.
In TSFS, the jocular exchange between Scotty and Kirk that some see as Scotty confessing to long-term lying about his estimates is really nothing more than some good-natured joking between two friends based on their shared opinion that repairs that should take eight weeks by the book, Scotty can do in two.
It is not until Scotty's guest appearance on TNG that he becomes someone who thinks of starship captains as children who need to be lied to and "handled" (assuming one doesn't interpret that whole scene as him simply pulling Geordi's leg). Personally, though, I think it's wise to take the TNG-and-later writers' interpretations of any of the TOS characters with a grain of salt.