Our IQs are similar [or] about the same. By the way, cleverness and IQ are two different things.

I am as intelligent as A. (or a group of people)

"Is this ok? We have a similar IQ." That is fine with grammar and sentence structure but it is not a fact that people's intelligence are all equivalent given that personal intelligence varies greatly.

"We have a similar IQ."

No one ever says "we have similar IQ" (unless you are talking about the results of a test) but you could say we have equal cleverness, or "I am just as clever" or "we are both clever" or "we are both smart" if you wish to compare intelligence. In that regard, you might say "We are both intellectuals" if you are trying to say you are both a high level of intelligence.