smartChord allows individualized tone names and symbols. You can define your personal preferences in the general settings. These settings affect all of the smartChord features.
The songbook e.g. converts the chords and shows them according to the general settings. So you’ll always get a C#, even if the original chord of the song is written as Db. But there is an option to force the songbook to show the original chords. But keep in mind, that with this option activated, the transposing is deactivated!
There is also an interesting setting for the chord diagram info in the instruments ‘Chords’ settings. It allows to switch between the tone symbols, you have chosen in the general settings or the tone names according to the music theory.