What plugin format should I download?

• Are you a Pro Tools user?
  If you’re using Pro Tools, then install AAX plugins.
  
• Do you use Windows or Mac?
  If you’re a Windows user, then install the VST3 plugins. On the contrary, if you’re a Mac user, install the AU plugins.
  Although Mac now supports VST3 plugins, AU plugins give Mac users a better user experience.
  Some DAWs on Mac only support VST3, like Cubase and Bitwig Studio, download the VST3 Mac plugins if you're using these DAWs.