When looking for clean roms, you should basically steer clear of most square bracket codes, with the sole exception of [!]:
[hXX] are hacked roms, in practice just a hacked header is enough to warrant this label.
[oX] are overdumps, which will work but as the name suggests contain redundant data.
[!] are verified dumps, which is a Good Thing™.
On a related note, the policy of including even known bad dumps in GoodTools is the exact reason why many people have switched to NoIntro sets, which contain only proper dumps.