That would be weird. Even if we assumed that human-like intelligence is the smartest possible architecture, there are many ways to improve the performance within essentially the same architecture.

Imagine that we scan a human brain, atom by atom, and create a computer simulation of it. (If you believe that brain alone is not enough, let's simulate the whole body.) We would get, essentially, a human living in a simulated world. Suppose we simulate one of the smartest ones.

What if we increase the speed of simulation? Human brain runs at cca 100 Hz, because the signal is translated from electric to chemical and back to electric at the end of each neuron. So either we simulate this entire process, only faster, or if possible, we make the signals between simulated neurons run much faster by cheating at simulation. Imagine having a human, only 1000× faster.

Now speed is not the same as intelligence. A 1000× faster fool would still be a fool. But a smart 1000× faster simulated human could solve in 3 seconds a problem that a normal human could solve in 1 hour. Or solve in 8 hours a problem that a normal human could solve in 1 year. So we already got something that normal people couldn't compete against, intellectually.

We could optimize the metabolism of the simulated human. Because he only exists in the computer memory, it is not a problem to e.g. regularly scan his entire body and remove all cancer cells. Similarly, remove all physical damage, including aging. So it would be a (1000× faster) immortal human with perfect health. In a month, he could learn as much as a normal human during entire life... but then he could still continue learning, while the normal human would die, and his descendants would have to start learning from scratch.

And instead of one person we could simulate thousand people. Each of them could become an expert on a different area, and they could help each other. The simulation as a whole could study and research many things in parallel.

So, from outside, we would see a huge machine that in one month can understand almost all human knowledge, and then proceed further in all directions. I suppose this qualifies as "smarter than human". (And this still assumes that human-like architecture is optimal, which in my opinion is probably not true.)

Imagine you had 5% of your intelligence and a million years to think about things. I would for example love to take on the hard world problems or [hell] become a prepper! Reality has it that I haven't the life span to be sufficiently serious about these things. We barely have time to be serious about a single thing.

What if fairies could grant us wishes. Sorry I don't mean to be facetious, but all you're doing is pre-supposing an answer. That's not helpful in working out what the answer actually is.

I disagree. I think questioning assumptions can help you come up with novel solutions, because you don't assume you're already looking in the correct place.

Asking the question "what if we're at the limit for intelligence already?" provokes the answer "but we could always speed up the thinking process and create a faster brain, which would create better intelligence". But this assumes that faster thinking will definitely result in better intelligence. What if the human brain works less like a computer and more like car traffic, where more speed doesn't necessarily result in more throughput? Maybe there are other factors we need to consider besides speed. What might those be?

This, to me, is a valuable exercise. Barring people from asking questions that don't propose solutions seems like a good way to squash creativity, to me.

Seems to be an unreasonable assumption given the many idiosyncrasies and shortcuts human mental architecture has. I can simply remove them and have a better implementation.

Humans are not thinking machines. We're reproduction machines. Thinking and problem solving are just an emergent features and not by design.