Unofficial - TheIndex
Official - /r/anime list of legal streams
Streaming sites require no setup and are convenient. However, they heavily compress video and may have ads. Aiming for compatibility, they are also unable to use efficient codecs like x265. If data limits are a concern, torrenting x265 mini encodes from nyaa is a better option. Here is a comparison between mini encodes and most popular streaming sites - https://slow.pics/c/pjYaqdnr.
Official streams have better quality, but are also larger (~1.3GB per episode for 1080p). They can be obtained by torrenting from groups like SubsPlease, who rip untouched official streams.
Read more: Quality Guide
The downloaded .torrent file or the magnet link has to be opened in your torrent client - qBittorrent for PC and LibreTorrent/Flud for Android. After the download is complete, the torrents do not need to be removed from the client.
The speed is dependent on the number of seeds and their connection quality. You can connect to more seeds and improve speeds with port forwarding. You may want to use a VPN or a seedbox for downloading torrents to avoid receiving a copyright infringement notice from your ISP.
Advantages of torrents include access to more options with better quality/size ratios, and automation through RSS or Sonarr.
VLC is not recommended because it displays wrong colours, introduces visual artifacts, and breaks intensive subtitles.
Read more: Playback Guide