You need only to install one of the versions.
The different is:
Version 1:
You must define a new navbar-menue-item everytime you install a new language and want to make it selectable in the navbar
Version 2:
The installed and selectable languages are detected automatic, no need to add new navbar-item when a new language is installed
Version 3:
One of your languages is the default-language. Every visitor who comes first time to your board will see the board in this default-language. Version 3 detects the language-settings of the users browser and automatic set the vB-language to this language if available. Example: Default is English, you have installed English, German, French, Spanish. A user with French language-setting in browser come first time to your board, he will see it in French. No need for him to select the language of your board manually.
I hope your confusion is gone now
Best regards
J?rg