Well, all "feminizing treatments" including NBE tend to have potential for some negative effects "down there." However. there seem to be large variations between individuals and medicines/herbs taken.
Regarding milk production: Prolactin promotes it, but has also some negative effect. One research article related to it:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6859666/
That article concludes:
"We found no obvious relationship between erection time at penile tip and prolactin levels, but observed a negative correlation between base erection time and prolactin level (hazard ratio: −2.68; 95% confidence interval [CI]: −5.13–−0.22). With increasing prolactin concentration, multivariate analysis showed obvious reduction in base erection time among patients with normal Rigiscan results (hazard ratio: −3.10; 95% CI: −7.96–1.77;
P < 0.05). Our data indicate that prolactin inhibits penile erection, particularly at the penile base. In addition, when the effective erection time of the penile base lasts longer than 10 min, prolactin has a more obvious inhibitory effect on penile base erection."
To me the result doesn't seem to be too dramatic, but the trend is quite clearly visible.
It is a choice between two things which are difficult to fully combine. To get something you risk losing something else. And "your mileage may vary" because our bodies react often quite differently to hormones.
-Teddy