Why would anyone rip to AIFF in this day and age? It's a waste of storage space. ALAC is the perfect lossless solution when you use Apple equipment.
Ripping to FLAC level 6 is an even worse advice. There is no benefit in doing that. It's actually an even worse waste of storage than AIFF or WAV.
The beauty of lossless compression that it is really what it says on the tin: Lossless! There have been many experiments with lossless compression and transcoding. If you rip a CD in ALAC, transcode it to FLAC, transcode it to WAV and then burn a CD you will have a bit perfect copy of the original CD. It may actually sound even better if the rip is done with error correction on. Your CD player will have less error correction to do when playing. Error correction in ripping works much better than in a CD player because it doesn't have to be done on the fly. The basic principle is: lossless is lossless. Unfortunately there are still people who think the basic principle isn't true.
@millennia_one
I think you're right about the default setting in iTunes being 256 kbps AAC in the past. I started out with that before switching to ripping to ALAC when the prices of storage went down and integrated my Mac into the stereo system with an Airport Express. That was around 15 years ago.