FLAC format is lossless format meaning that regardless of the level of compression used, you will always have the real lossless audio. Higher compression meaning to a some extent the smaller file, but it will need more CPU power to play and compression time will be slower. Basically any lossless audio format (Monkey's Audio, OptimFROG, WavPack, Tom's Lossless Audio Kompressor (TAK) etc.) will give you a bit for bit audio in the same way as Tiff, bmp, PSD, PNG etc. will give you always the exact image. Regardless of how many time you open and save the audio file, result will be the same as when you're using the Wav format, just you will have compression.
At the other hand, you must know that when ripping CDs, the used lossless format will not have any influence on the sound fidelity, but the ripping parameters will have. CD/DVD device read offset settings, using or not using the CD/DVD drive cache, using or not the C2 error correction, ability of your drive to use Accurate stream (ability to avoid jitter) will have the highest and utmost influence on the ripped audio fidelity. What lossless audio format you will use after to convert the ripped audio from Wav (when ripped audio is stored in temp folder Wav format) is not so important
RR isn't bad, but for the extreme quality copy EAC is still better and it's the ultimate tool for this. I would advise you to use EAC (you can run it under Wine)