That "intuition" is not intuitive. How do I choose an appropriate reasoning effort?

I use these models all day long, experiment, and have no clue how to choose that.

It just showed up one day in the interface with no explanation or guidance. Its use is mysterious, its effects unclear except through intensive experimentation, and to this day it mostly seems "how many bad decisions will Claude go forward with when it finally dumps out screenfuls of text instead of getting better guidance early on" though it's certainly not a guarantee on anything.

These models are being released at breakneck speed even before their creators know how to use them. It's a big project of collective discovery to figure out what they are doing and how to use them.