@Faecon
I would suggest that we move the SpotifyPlus discussion to SpotifyPlus integration HA Community forum post for more help and information, as the detailed questions are off-topic for the current SpotifyConnect integration forum post. With that said …
Check out the Services Provided wiki documentation for a list of provided services.
Quick example of the Player Media Play Context service call (change the entity_id value to yours):
service: spotifyplus.player_media_play_context
data:
entity_id: media_player.spotifyplus_john_s
context_uri: spotify:playlist:6M8n0Sp9895BXEE0MbGPde