How big is a pixel? 7.4u, 9u, 12u squared. How many arcseconds does that pixel cover based on your optical configuration? What if you 2x2 bin your guider to boost sensitivity (i.e. turning a 9u into a 18u)? How does the guider pixel size differ from your imaging chip pixel size?
You'll find mount manufacturers judge their performance on peak-to-peak arcseconds. Arcseconds are a definitive measurement, pixel values are too variable and to be honest could mean absolutely anything depending on what your arcsec/pixel optical configuration is.
Keep in mind that guiding algorithms determine a star's centroid with sub pixel precision.
If you are looking for a bible on auto guiding, look no further than the attachment below. Jim McMillan is renown for his guiding techniques and code he has written including the MaximDL plugin
Multi-Star guide where you can guide on multiple guide stars to minimise chasing the seeing.