The playlists that were created in Tidal app, are duplicated in Naim one. Deleting any of doubles deletes both. So, be careful.
Note, that you sometimes you can restore the deleted playlist if you switch to Tidal app immediately if it was started before.
Workaround - creating Tidal playlist from Naim app gives the single instance.
Another issue - Naim app is unable to remove the track from the Tidal playlist when the track is somehow restricted in Tidal. An exclamation sign is shown on the track. Workaround - remove from Tidal app. These track are visible but can not be played by some reason.