Set in the Old Town amidst wonderful narrow streets and superb architecture it really is a lovely place to visit. There are very unusual Stations of the Cross and in the main most tourists give the cathedral the respect it deserves although you will always get the rude and ignorant who just want to take photos.
The church in the middle of Dobrovnik old town has a quite nice interior, but just moderately interesting. The treasury was open when we visited (free of charge). The room is full of glittering things containing so-called relics. Difficult to see more than the few things just in front og you.
Average church in the center of the old town of Dubrovnik, lovely but not so spectaculary. But Dubrovnik is a small city and surely you will visit this church.