Well, MP3s are lossy compression so from a technical standpoint they're very different from CDs.

If anything, FLAC files are closer to CDs than MP3s are because those are lossless, and of course WAV rips are raw, uncompressed rips similar to what you'd get with DAT.

No, but MP3s are closer to MDs or DCCs in that those are also lossy compression, with literally being an evolution of the codec DCC used (MP1) while MD used Sony's homegrown ATRAC codec, than they are to CDs, while FLAC is lossless so it should be the same as a CD with WAV or AIFF rips literally being an uncompressed copy of said CD.