Short adjectives (one or two syllables) can be placed before or after the noun, notable exception to this being BAGS adjectives as you’ve noticed. A lot of them have different meanings depending on their position, but there’s no general pattern to know the nature of this modification.

That being said, it seems that when the adjective is in front of the noun, it has often a moral or emotional meaning

Un curieux personnage -> An odd character

Whereas an adjective after the noun has frequently a descriptive meaning

Un personnage curieux -> A curious character

You can find a (non-exhaustive) list of adjectives which take different meanings here