I've been supplementing with B12 for the five years I have been vegan but only once or twice per week at 500 - 1200 mcg depending on the supplement, with occasional fortified plant milks or vegan yogurts. I had my B12 blood level checked a few weeks ago and it came back at a healthy 619 pg/mL which is in the middle of normal range. I'm guessing it would have been lower if I had not supplemented occasionally. I have never supplemented with it daily. One bottle of B12 can last me four or more months.
As far as soy, here is a comprehensive medical study and analysis of phytoestrogens, including Daidzein and genistein that is found most predominantly in soy. Keep in mind that phytoestrogens are found in a wide variety of plant foods, such as leafy greens, flaxseeds, and other beans. Daidzein and genistein are the most concentrated forms of phytoestrogens. Also keep in mind that the studies referenced in the link below used human doses of concentrated phytoestrogens (isolated from their natural environment in concentrated amounts) and greater on rats, far beyond what would be healthy for a rat. So the studies are a bit biased.
In moderation, soy that is found naturally in plant foods such as edamame, tofu, tempeh, and miso is perfectly fine. It has benefits that shouldn't be dismissed, such as iron, protein, omega 3s, and calcium. Fermented soy foods are excellent for healthy gut flora. No need to avoid soy altogether unless one has an allergy to it, or is being treated for breast cancer.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074428/
The only other supplements I personally take regularly are vitamin D (vegan version) and calcium, and only for medical reasons (I am on a shot for osteoporosis that was diagnosed in 2006 via dexa scan, years before becoming vegan). Everything else I have gotten from food. My hemoglobin also recently tested very healthy at 13.7 g/dL (normal range for women 12.1 - 15.1) and I have never supplemented with iron. Plant foods such as beans, leafy greens, black strap molasses, and some whole grains (all staples for me) are abundant in iron.