Merge Spotify and iTunes playlists

[ajw88]

If I import my iTunes playlists into Spotify to play offline will each track be dulipcated on my phone / take up double the space? Basically, I'd like to add tracks that are already on my phone in iTunes to playlists on Spotify and then be able to play the entire playlist offline. It's odd; the 'local files' folder only has tracks that I've mistakenly saved to Spotify that were already also in my iTunes library. Also, the last folder of the playlists tab is called 'iTunes' which must be an auto-generated folder. Anyway, this folder seems to contain all my iTunes playlists but above each playlist there is still the download switch indicating that the files have not yet been downloaded to Spotify. Weirdly all my iTunes playlists are present in this folder, even those that aren't synced to my phone. Something to do with iCloud maybe? I really don't know. Anyway. If anyone can help with / explain all this I'd really appreciate it. Thanks in advance