My personal experience has been dramatic:

5/6g a day.

Very demanding job with lots of ‘thinking’

3 times a week gym

Pre creatine I would struggle to maintain ability to do the hard thinking around 3pm. Just like, fog or I could feel my brain didn’t have capacity.

Now, I am capable till the end of the day. Feels like a well trained athlete at the end of a game being able to deliver rather than just holding on.