T. kiusianum does not have peltate leaves. Your plant in question does. According to Aaron Floden, an American botanist and Thalictrum expert, T. ichangense is rather rare in cultivation, and T. coreanum is the usual imposter. They are quite easy to tell apart once established, as T. ichangense will remain a clump, while T. coreanum has a spreading habit by underground roots and tubers. (I believe T. ichangense produces tubers also, but is not mat forming.)
Notice also that Thalictrum 'Heronswood Form' does not have peltate leaves.
My T. coreanum usually has light lavender flowers, but sometimes are white (unless you look
really close). They always tend to have darker color in the early part of the bloom season.
