I have a manuscript in which the main character is smarter than me (better SATs scores than me too, curse her!). Although the story is fantasy, there is a significant mystery/detective element. While I would have eventually come to the same conclusions as my MC, she figures things out a lot faster than I ever could have and reacts much faster.
I asked my beta readers if they came to the conclusions faster than my MC, and if they were able to follow her logic. The response was unanimous, they were one step behind the MC but could understand the reasoning, but sometimes not until after she had taken action. I considered this a success. I am sick of reading stories with supposedly genius characters when I have been way ahead of them. But I think it all comes down to pacing, how much information you give to the reader, how long it takes your characters to reach the right conclusion etc etc. I don't like mystery novels in which key elements or clues have been withheld to make the MC SEEM smarter, seem quicker on the uptake.
I think the best way though, to see if your MC is quick enough and smart enough is to get reaction from beta readers. It is hard, being so immersed in your own work, to see how obvious or subtle clues can be. Some things I thought were obvious ended up being the sort of thing readers did not pick up on and vice versa. And of course, everyone reads a little differently so the more beta readers who give you feedback the more you can safely infer how your work/MC are being interpreted.