Is MPEG-4 Linear PCM 2ch 48kHz/16bit good, very good or bad sound quality?

Mmm J

It depends on the audio quality when recorded. Both Iridflare and spacemissing are correct.

spacemissing

It is Excellent! (slightly better than CD) Any linear PCM codec is to be preferred over any lossy codec such as MP3.

Iridflare

Unless you're expecting dogs or bats to listen to it, that's fine. 48KHz means you can play back up to 24KHz (well above human hearing) and 16 bit depth is plenty for normal uses, though pros use 24bit.