Breaths and add ons won't really help with the realism. At most with adding stuff more pitches will help since UTAU will have more to work with, but your best bet for a realistic sound is a good oto
I second Sors’ reply! Also I want to add that to increase realistic-feeling to CV voicebank that how you voice and record your samples are as important than sound configuration oto.ini. Samples that are made from singing-like voice turns out much realistic sounding than spoken-like. Here is a good thread about answering about voicing question: https://utaforum.net/threads/speaking-and-singing-utau-difference.19553/#post-137076
