Low resolution will give either fuzzy edges, or a pixelly appearance to the image.
Spatial resolution is defined by the size of the imaging voxels.
Since voxels are three dimensional rectangular solids, the resolution is frequently different in the three different directions. Assuming everything else is constant, increasing the number of frequency encodings or the number of phase steps results in improved resolution. The frequency encoding depends of how rapidly the FID signal is sampled by the scanner. Increasing the sampling rate results in no time penalty. Increasing the number of phase steps increases the time of the acquisition proportionately.