"Smartness," and "intelligence," are distinct. While many smart-humanoid(s) are likely to have higher IQ's; all specimens with "high IQ's," may/may not be smart. Do 'extremely smart persons,' exist? - indeed, and most are simply highly educated specimens in a specific field of study or a specimen who has much accumulated knowledge about anything - not just 'correlative' data; nor easy access to knowledge sources (re: experts), but knowledge of (X)—which is for ex; a sufficiently useful tool for determining which doctor to select, and which to be weary of, however most do not have the acquired knowledge themselves to distinguish smart (re: knowledge of X) - from specimens who are heavily & critically relient on hueristics (knowledge of how to use the knowledge of (X) that exists). I would consider a humanoid with a Ph.D (& demonstrable knowledge in their area), e.g., physics, psychology, zooology, economics, mathematics, linguistics, or even the fine arts, such as music (re: mastering an instrument / composing music), someone "very smart".
I would consider a humanoid with a "high-IQ," someone highly intelligent (re: advanced problem-solving / fixation on lose/lose conflicts - solving irresolvable problematic conflicts) skill(s)). There have been plenty of 'average-IQ' humanoids with "smarts" and noticable wits. If you have both (a very smart humanoid with a HIGH IQ), I would consider the specimen along the lines of ('Hawking'). I do not think Hawking is only just, "subjectively," smart/intelligent, and most specimens would recognize him as "objectively," above the rest. If by objective, you mean POV-invariance.
Anyway, most specimens have the capacity to be smart people with average IQ's - and 'stupid' (i.e., reliance on knowledge illusions) with high-IQ, and et al. There are also 'objectively' low-functioning specimens with low IQ and very little "smarts," which most specimens haven't anything to worry about in regards to themselves, for ex; such a specimen is utilizing PerC without any major complications, I reckon they are relatively average in IQ & functional, with a capacity to be at least, be somewhat smart if the specimen applies themselves. I am sure if any such humanoid was only just very dumb (re: Low IQ & no capacity to be/gain smarts) - this would have been easily determined/addressed somewhere [in early childhood] (re: lacking the capacity to develop / problem-solve simple hiccups on the environmental terrain) which as pointed out earlier, isn't simply inability to academically keep up peers, but malfunctions with effectively and/or reasonably interacting with them as well, (i.e., severe behavioral problems) and Neuroplasticity is also a considerable factor to consider when considering other spectrum such as (age).