The CK7 is good, very akin to the ER6i in terms of sound IMO with minor differences mainly in the bass (ER6i extends deeper and is slightly more detailed while CK7 is punchier).
To the basshead, the CK7 will sound thin.
The CK5 is utter rubbish, it feels as if it has no bass and the entire frequency spectrum feels downtuned and muddy.
CK31/32 slightly improves on the CK5, but even given their price point of US$19 where I live, I find it hard to recommend them over the likes of slightly more expensive budget semi-canals like EP630 and -> Cresyn LMX-E630 <- [rare item?].
Isolation wise, it'll be what you'd expect from a semi-canal, sub-standard compared to IEMs, but they still get teir job done OK-ishly without having to push your volumes to ear-splitting levels.