This varies with technology. With FDM, DIW, and robocasting, the nozzle size and minimum positioning will vary, but will not come close to a good SLA system, where pixel size is really your only limitation. With SLS, beam size at focal distance will be the limiting factor. If you're using an ink jetting technology, the XY resolution is very fine (think of your inkjet printers), but different units will have different minimum Z movements.