I have a few simple questions about Feynman Diagrams:
1) Why, when $W^+$ or $W^-$ bosons are involved, sometimes the sign + or - is shown and sometimes not ([example1](https://media.springernature.com/lw685/springer-static/image/art%3A10.1140%2Fepjc%2Fs10052-018-6399-3/MediaObjects/10052_2018_6399_Fig1_HTML.png?as=webp), [example2](https://it.wikipedia.org/wiki/Kaone#/media/File:Kaon-Decay.svg))
2) Why the arrow is usually not shown on bosonic lines?
3) Sometimes I have the impression that for a single process, different equivalent Feynman diagrams exist. I give an example below. How can I decide in this case if the two diagrams have to be take into account or not? Is there a general rule?

[![The only difference is in the central top quark][1]][1]


  [1]: https://i.sstatic.net/C3DV2.jpg