No feminizing effects if your isoflavone intake is equal to that of average Asian male
https://www.ncbi.nlm.nih.gov/m/pubmed/20378106/

Feminizing effects reported on individuals that took 9x isoflavones (360mg/day) of average Asian male intake.
No reported increase of estrogen level even when males took 150mg/day of isoflavones
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5188409/

"It should be commented that, being estrogen analogues, phytoestrogens may exert estrogenic effects on their own independently of the levels of endogenous hormones"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270274/