Both Tidal and Spotify do allow downloading music for off-line listening. I've only done this with Spotify. I have no idea what the "professional Spotify Playlist Downloader" is. I'm certainly not using such. Whole albums or individual tracks can be downloaded. Downloading and offline availability isn't limited to accessing a preexisting playlist. Downloaded files can be accessed via laptop, iPhone or iPod. If you are happy with how things are working now...great. If you are running into limitations with your current method, see if this helps.
https://support.spotify.com/us/listen_everywhere/on_phone_tablet_desktop/listen-offline/
https://support.spotify.com/us/listen_everywhere/on_phone_tablet_desktop/listen-offline/