Ive never used those ratings but supposedly the overall means nothing. All that matters is the individual position ratings which are spaced out for everyone. And also the speed plays much differently with these because its more based on acceleration not top speed which is the case in a real game.
Realistically the NFLs all about opportunity. There are a few guys that are so much more talented than everyone and could fit in any system with any level of talent surrounding them but after that top tier its all about opportunity, being in the right system and work ethic. So IMO people should be all relatively close together rating wise