Both the C#/D and B/C configurations have all the notes of a 12-tone scale available, and can be played in many keys. Not all keys are easy, though, and the bass chords available would limit somebody who actually plays them (many players in the Irish style play basses very sparingly or not at all).

On multi-row in-out boxes: these are generally tuned "equal tempered" because it doesn't make sense to tune to a preferred key (as in "just" tuning or Cajun tuning) if you're going to take advantage of the multiple key possibilitys of the 3-row.

Therefore, even a LMMH four-reed triple row isn't going to sound quite Cajun if the tuning is equally tempered. Happy 4th!