Wonderlic score. I do think a bad wonderlic score, especially for QB can be foretelling. But a very high wonderlic doesn't really predict anything. If anything, super studs seem to fall into a sweet spot of 25-35ish (out of 50). It's almost like to be great, you need to be smart enough, but not too smart as to over-think a situation. Sort of makes sense in a game of inches.
I think that's more a case of some super smart QB's being able to mask/overcome their physical deficiencies better than their less smart peers. But the NFL doesn't afford much opportunity to hide something forever. At some point some DC is going to make you do that thing at which you are not so good. And then everyone else copycats it.
I think you hit on an accurate point about a minimum threshold. But I think you are off on the ceiling threshold concept. It isn't about being too smart anymore than it is about being too fast. I do think the high threshold is just like the low threshold in that a very high score or a very low score is by definition an outlier. So the chances that someone would have a very high score or a very low and still have good enough ability in other attributes to be successful is going to be an even smaller subset of that initially small subset. So it's more a situation of how many stupid guys are going to also have the athleticism to overcome that stupidity and how many of the smart guys are also going to also have the athleticism to utilize that intelligence.
So having a high score isn't a detriment. It's just that there aren't many guys that have both a high score AND the other talents to make much of a statistical dent in the apparent trends.
I tend to think the 40 is over-valued for a projected bell-cow or 3-down back and arm strength is over-valued in QB's. In both, it isn't that they don't matter. They do. But it's more about needing to have at least a certain level of it, but once you get over that level, other factors start to separate the wheat from the chaff.
I think if you run a study of the metrics, you'd find a range in any attribute where the historical studs at a position fall.
But the problem is, there are also going to be a tremendous number of duds that also fell in that range. So that, I believe, tends to support the threshold theory. You need to have at least a certain amount of something to be successful, but the presence of that thing still doesn't guarantee success. Falling outside of the range helps in predicting failure, but falling within the range doesn't really help in predicting success in a choice between multiple contestants.
So when draft day comes, you might be able to exclude some player from consideration because he falls outside those ranges, but you still have to make a call between multiple guys who do fall within that range, some of which will be hits and some of which will be misses.
I think the height and weight numbers are over-used as well. How many times do we see a player's name, then his height and weight listed, as the sole descriptors in the news blurb or list? It's almost like a name - rank - serial no. type thing. Like we're thinking, "He must deserve that new contract because he's _____ tall and weighs ________!" or "I'm drafting the ______ tall RB who weighs ________."