Pueraria Candollei variant Mirifica (shortened to Pueraria Mirifica) is one of three herbs given the title of 'Kwao Krua', and is known as White Kwao Krua. This herb has been traditionally used as a vitality enhancer and rejuvenating agent particularly for older women. It should be considered a different supplement than Kudzu root, Pueraria Lobata.
When looking at the herb, it is a great source of classical phytoestrogens (including the soy isoflavones) but contains a class of phytoestrogens known as Chromenes that rival estrogen itself in potency. The herb is highly estrogenic as a result, and is considered the standard herbal 'estrogen replacement therapy' due to its potencies.
It has been tested numerous times for reducing menopausal symptoms (as estrogen replacement therapy itself is quite effective), and despite the universal promise it shows many studies are not blinded and not run against a placebo; on the topic of menopausal symptoms, this is a significant problem as placebo can be very potent (see Black Cohosh as an example, as the placebo effect in menopause has been reported to reach up to a 50% reduction in symptoms).
Based on the preliminary evidence, it does appear promising and effective (although it is much less supported than Vitex Agnus Castus for menopausal symptoms). There is currently no evidence to support the notion that this herb is somehow safer than estrogen replacement therapy, so their benefits and risks should be seen as interchangeable for the time being.