I don't know what the rate of twist is...I think that the manufacturer could best answer that particular question.
As far as what load your particular rifle likes, the only person who would know is you. Why? Well, every single gun is different. They look identical, but they don't act identical. What may group well in your rifle may or may not group well in an identical rifle.
That said, there are bullets that are "generally" more accurate than others. I have found that my Tikka in .243 likes Federal 100 grain premium boat-tails - groups around 1/2 an inch.
Best thing to do is shoot different ammo and see which loads it likes best.
Zachary