I came here to say the opposite. Running on MacOS 15.7 the original Client uses ~200mb and Fastpotify uses ~500mb playing the same song while being substantially slower when navigating music.
EDIT: I forgot about the Spotify Helper processes - taken into account the original spotify needs ~1GB.
However it's still a lot faster than Fastpotify
EDIT: I forgot about the Spotify Helper processes - taken into account the original spotify needs ~1GB. However it's still a lot faster than Fastpotify