As you can see, Space Angler has the sharpest turning, followed by King Meteor, Elegance Liberty, Astro Robin and Twin Noritta. Elegance Liberty is a good choice for GP mode, since it has a B body and doesn't lose a lot ot speed from turns like Space Angler. Its top speed and boost aren't that good though.
You could also go for a machine with slightly worse turning but better top speed and boost, such as Deep Claw, which also has a B body. However it does lose speed from wide turns so be careful of that when you're not boosting.