Yes you can over pitch, pitch the correct amount for best results. However it's not as sensitive as some believe. If you need 350 billion cells and pitch 353 billion, no problem in my opinion. Pitching 700? Probably way too much.
From what I've read and heard and experienced, pitching too much can cause the yeast to go dormant too soon because they think there's not that much work to do. Well, they don't THINK, but that's the end result.
Personally, I use a good pitch calculator and translate ml to cups, and I round off to nearest quarter cup