Higurashi question...?

Well, Higurashi no Naku Koro Ni Kai explains everything about why we have so many different story arcs usually unrelated to each other or parallel to one another. I think you should watch the next to truly understand why everything is set up the way it is. With Rei & Kira, well, their more or less fanservice but you can watch them if you wish to. Kaku isn't out yet so I'm not for sure about that one yet.

Honestly, you should Try reading the manga. It goes much more into depth on the characters and their stories. It's also more bone chilling.

If you continue to watch it will help clear up your confusion. To me i really liked the firsr season but i like it more after i watched the 2nd because it made more sense. Overall its a good anime.