The Plug-in and the families are available in 3 languages: Portuguese, Spanish and English, and you can choose the preferred option when registering.
The language of your account is selected when registering, each account can only have one language and that will be the language in which the plugin and families will be displayed.
When selecting a language, remember that families will also be in the selected language, so select the language you prefer to work with.
If you have selected the wrong language when registering, the only way to correct it is by contacting Blocks' support team and requesting this correction.
Should I select the same language as my Revit?
No, you can have Revit in English and the plugin in Portuguese, for example, or in the language you prefer, regardless of the language you use in Revit.