Here are some useful informations about Green-bot Premium
Green-bot's main features are free but you need to vote for some commands that uses more CPU power than the others. You can bypass the vote-locks and access to some exclusive features with the premium.
Possibily to set a default track announcement channel
Automatically shuffle spotify/youtube playlists
Can change the speed of the music
Change the pitch of the music
Acces to 4 new filters
Unlimited queue size
Access to a new bot with better quality and stability
You can unlock all these perks with the Guild premium tier. You can have it for 1.50$ per month or 20$ per year if you pay actually!