Nim as a replacement for Python makes sense to me. We often hear that many Python developers went on to choose Go when needing more performance, but Nim feels like an easier move.
Nim not only faster than Go but have a very similar syntax to python. It make more sense for Python developers to use Nim when need more speed instead of Go.
Nim code also tends to run faster than Go code (in my experience).
I didn’t meassure, but I also don’t have any experience saying otherwise. Both are great languages and depending on the problem I’d be happy to use either.