I've had good luck with PacNor barrels. IMHO there are better barrels but definitely none that offer so much accuracy per dollar.
As far as twist, what bullet do you want to shoot? I would suggest going to Shilen's and Berger's web sites and see what they recommend for twist.
I don't like a twist any faster than is really necessary. Faster twists generally increase bullet deformation, increase pressure, and foul more because there's more inches of corner to hide "stuff" in.
Flex is for people who don't have lockers.