When creating a Soundiiz account, you can use directly your email and create a password but you can also a social profile or directly use a music account.
Be aware when creating a Soundiiz account using "Sign in with Spotify" or any other music service, we will directly require more scope/access than necessary for the login. However, that allows us to directly connect your music account to Soundiiz and display your playlists, albums, etc.
Soundiiz is not only a tool to transfer your playlists between music services, but also a music account manager, allowing us to delete elements, update playlists, retrieve your favorites, etc...
API scopes required by Soundiiz are large due to all operations Soundiiz can support.