Hi dear,
Great to hear that you are trying to be on a caloric surplus. That is the best way to go on NBE.
Both PM and BO are hormonal 
" alt="" title=""> , but don’t worry if taken in adequate amount they tend to regulate hormones, it’s only if you take too much that things can go out of whack. As for safety, the ovaries are far from the cow brain so don’t worry about Mad cow.
You need to do BO between 3-6 months before you can really know if it’s for you or not
You should be able to see some non breast changes within a month.