A FLAC file is a good as the CD from which it was ripped. No better, no worse. CD data is 16 bit/44.1 kHz (Redbook), so the actual sound is never going to be better than that. That said, the sound you hear from the CD will often sound more natural if it is mastered at higher bit and sample rates, which is why I sometimes buy re-mastered CDs of music I already own.
SACDs definitely have better sound than regular CDs, but you’ll only hear those improvements on a high quality surround sound system. SACD tracks can’t be ripped to a digital format for listening on music players, but since headphones are inherently binaural and have limited dynamic range, a Redbook track from the same master as the SACD track is just as good for that purpose.
I mostly listen to music on an MP3 player these days, but I have thousands of CDs - about 2/3 Classical and 1/3 Jazz - accumulated over more than 30 years, and I’ve probably given away nearly as many over that time. When I buy a new CD, I rip it to FLAC and then convert it to MP3 for listening. Most of the older CDs only get ripped when I want to listen to a specific one. The FLAC files get archived onto DVDs for storage (about 10-12 CDs to a DVD). The MP3 files stay on a hard drive. I keep everything organized by using one folder for each CD or multi-CD set.
I use
Easy CD-DA Extractor for both ripping and converting. The final product of my own rips is HQ VBR (EZCDDA uses the latest LAME encoder), but I have MP3s obtained from other sources which can vary from 128kbs to 320kbs. Given the same source, higher bitrates sound better, but in my experience, the quality of the original source is more important than the bitrate. MP3 encoders also vary in quality – LAME has improved greatly over the years, but I have been surprised at how well music encoded some 7 years ago with the Mediasource software bundled with my first Creative player still sounds today. Variable bit rates save space over constant bit rates and don't seem to affect the sound quality on any player I've owned.
The most reliable online CD database today is
Musicbrainz, but the quality of data retrieved is still variable. I use
Mp3Tag to edit tags. Among other things, it lets me export and import tags to and from text files. I often find it faster to export a lot of tags and edit them in a text editor, then re-import them. That also makes it easy to re-use tags from one rip to another of the same material, or copy them from other versions of the same works (particularly useful for classical music).