Zbrush uses catmul-clark subdivision, so there is an even distribution of polygons, provided you stay away from 5+sided ngons on your lowers subdivision level.
Mesh optimization would only be calculated after you are done sculpting, not at run-time, because the way most (if not all) optimization algorithms work, it'll destroy the underlying topology in such ways as to make sculpting impossible... And it has a great tool for this, called Decimation Master.
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