I'll give you a Pro and a Con on this.
1. Soy estrogen (produced from non-GMO soybeans) is "phyto-estrogen" meaning plant-based, or natural. Soy actually saved me during menopause. Because I have chronic lymphedema in both legs (slow lymph flow) + cervical cancer past, I opted not to take drugs containing estrogen derived from horse placentas, for instance. Yuk!
Anything plant-based has lower side-effects, not more.
That said, women (or men) who have *breast cancer, or are at *higher risk*(genetic) for it, should AVOID Soy milk, in my opinion. Almond or some other may be a better choice. But as you said, watch estrogen level if concerned. Otherwise, Soy milk (non-GMO) is an excellent product.
From my research this year, I am convinced that we are at a much higher risk of disease from some of our food supply, especially here in the USA where over 80% of our food & seed has been Genetically-Modified for past 30 years. This includes wheat, corn, and dairy. I personally believe chickens treated with hormones (for faster production) are a much more valid reason for early onset of puberty, and possibly the massive increase in breast cancer. However, this is just my personal observation.
Here's a site I believe you will like. The person who tweets for them posts compelling articles about how our food supply is being manipulated by Monsanto, now big banks and pharma. (I think SOR are Indian, coincidentally-not sure though. Their website is www.SeattleOrganicRestaurants.com
Their Twitter handle is: @OrganicLiveFood.
Thanks for your comment, it was a good question. I hope this helps.