Whether the contemporary UU focuses on reforming the self or society seems to me a concern about how an individual's way of living impacts others..
The idea of individualized transcendence seems to be analogous with the perceptive of Emerson's contemporaries who believed that the reform of the self was a form of a conferred spiritual democracy. Conferred because in theory, perhaps they could label it a spiritual democracy. Yet, looking at the historical events of the time where, for example, blacks did not have equal rights to resources, for a black person of the time, such liberation if it existed would be rather aloof. While some Unitarians argued that the self is the part of the society, and that therefore
reforming the self would effect desirable and seemingly positive outcomes in the community, I, like Margaret Fuller agree that focusing on the self could lean egotistical. This result would be harmful to the society if the self in question had hedonistic views, which if observed globally could potentially bring more harm than good. as opposed to, say, Henry David Thoreau's living lifestyle adopted maximally -One person wanting to drill a mine and others joining in order to support their families would be a great source of income while have devastating long term effects on those living on subsistence farming.
So, should the UU reform the self or the society? I would respond from a Kantian perspective and say that it would depend on whether or not the reformation in question was a corollary to that which is globally good, which good bring even more questions. That is, Thoreau living minimally in the woods is different from Thoreau digging a mine. Thus both maxims adopted generally could affect the society or individual positively or negatively..