Is Teru Mikami on a genius level of intelligence like Near and Mello?

Answer 1

As a kid he got into a lot of trouble (just as stated in the manga itself) and he always searched for a "God" who is making the world better.
He found it in Raito, which killed only criminals at first. Teru obviously looked up to him for punish those who hurt or kill people or cause them any other harm. You could say that Teru saw Raitos actions as revenge against those people who tortured him when he was younger.
Not knowing Raito aka Kira personally he never got that Raito actually gone mad. At the showdown-scene in the "Yellow Box" you can see Teru losing his faith in Raito when he finally realised his Gods madness. He refuses to help him. That may be an intelligent action. But you can't compare him in any way with Near or Mello since those two are / were really at a genius level.
Besides the fact Teru obviously had no problem with killing people which is, even if it's kind of "justifiable" because they were mostly criminals, at least very stupid due to humanity and human rights. It does not suit the goal he actually was searching for. And losing the way of what you want isn't very smart either, is it?

About the facts: Death Note 13 - How to read states that Teru has a level of intelligence rated 8 out of 10. Near does have 9 out of 10 points, Mello is rated with 7 points.

So you could say Teru may be smarter than Mello BUT (here's the point) Teru does not use his intelligence, he does what Raito tells him.

Summary: So you can say he's on a genius level just as Near and Mello but in real he's not smarter than these two since he don't use his brain anyway.