where to get CUE Sheets and M3U's

Yes. Kohlrabi did not qualify his statement with any limitations, so it applies to all methods of storage. Sure, you’d need a cue-sheet or some other method if you wanted to demarcate tracks for a single-file image, but it would still play gaplessly in any case. And nothing stops capable players from transitioning seamlessly between tracks that are stored as separate files; given a sane format, it’s trivial, and it shouldn’t be affected either way by whether or not you have some textual file saying ‘Oi, these tracks go together.’

You may find it enlightening to simply try these things rather than asking. Do your phone and player support gapless playback, with or without sundry playlists? Test it and see.