I think it's pretty reasonable to use Maths and hard sciences as a better rough indicator of intelligence than arts. People are talking about how some people who are great at maths might be terrible at some other things. That's a characterisation of maths savants that doesn't really apply to most people who are good at maths. Generally they don't look at a problem and think "this is the solution", they use knowledge, sound, self aware logical reasoning and tenacity to find the solution. It's far more common for someone to have an artistic talent that just doesn't reflect the rest of their intelligence. You might be able to write an emotive story, tell a funny joke or whatever. I think it's a lot more common for people with great comedic timing, drawing skills and geography degrees to be totally useless in the "real world" than it is for a talented mathematician to be.
I don't know who the most intelligent TSR member is, but over the years a few people come to mind. In no particular order, littleshambles, EierVonSatan, DanGrover, MSB, Melancholy and Drogue are all intelligent and happy to come across that way on here. Then there are others who are obviously extremely clever (from their achievements) but just use the forum as a chat forum so nobody would really know it. FadedJade springs to mind, Mr Fox back when he posted and I would probably put myself in this category (I have no achievements but I hear my internal monologue so I don't really need them to think I'm smart). I would also bet that Arturo Bandini over in the fitness forum is smart but it's hard to say since he only makes one line posts (there are probably thousands of TSRers like this.
I have never really talked to any of the hard science types here, so apart from EVS these are all artsy type people. If I know you and you're not on this list (failingatm for example) then lol sorry thx for trying.