My samples are: Humbug Finnish, Merino/Silk and Finn wool.
Now after all of this, I should also say, that your don't HAVE to do this. There are no spinning police. If you don't want to set the twist, that's fine, just keep in mind that your yarn will behave differently when working with it. If you want an energized yarn then perfect :)
Let me know if you have any questions and happy spinning!