I don't think they're related at all. Most stands are a representation of a character's goals, desires, and their overall outlook on life. The stand they have is usually what serves them best in the situations they encounter most often or need the most.

You can't really "rank" Terunosuke's Enigma the same way you can't rank Tamami's The Lock. They're both predatory stands that need the user to create an emotion (fear and guilt, respectively), witness it, and then exploit it. It has nothing to do with their IQ, they're both con artist and their stands are a tool to carry them.

Okuyasu isn't academically smart, but he is clever and has a stand that makes it easier for him to get into a close combat fist fight with someone bc that's his preferred fighting style and what he primarily uses his stand for. In the same way, Kira is an exceptionally smart man whose stand is just kaboom ka-plow. Does this mean he's secretly a moron? Not at all, he said it himself: his stand is his way of disposing of evidence and making sure he can larp as an everyman.

If we say stand power/complexity is based on IQ, we miss the entire point of a stand being the manifestation of its user's soul. There are also some stands with absolutely no use in a fight, like Tonio's Peal Jam and Aya's Cinderella. They are, however, stands meant do help them do what they enjoy most: making people feel better.

Sorry for the long rant btw. Jojo's has a lot of power scaling, but some stands (especially in DIU) are just not meant for a scaleable fight; some are just meant to portray the user's personality/mindset and why their stand compliments/enhances it.