Dragonball Z different versions
Firstly, there are several more adaptations of the Dragon Ball Z and not just the four you listed. However, the ones. Since that is not the main question, I won't elaborate on that.
To answer your first question, the Japanese version would indeed be the true shonen series and perhaps what Dragon Ball Z is truly intended to be. Being someone who personally dislikes dubbed versions, the Funimation dub is indeed very good and Bruce Faulconer's tracks make it an overall amazing experience. The Funimation dub that aired on Television was obviously heavily censored, however uncensored versions of the dub(Visually) have been released, however in terms of the script, there is censorship.With regard to your second question, DBZ Kai is different from the main version as it tends to remove filler episodes. Although, as far as Plot goes, there isn't any significant difference. With reference to Goku finding about Gohan, it wasn't really Censored. What is censored is mainly nudity, violence,  and random instances like these for example:  



The word "HELL" is replaced with "HFIL". Gohan's tears have been removed to make it seem like "Less of a Kidnapping". You can look at a list of censorship in the series here.