There are a few threads here on the EAC software you might want to peruse.
The FLAC codec is supposedly the same quality regardless the 'compression'... That does seem right too, though I still go with a 7.
I found another key for good ripping was to use CDs on the list of preferred CDs which have been used to calibrate better, the EAC software... it's along list so you probably already have these CDs.