Well... I have a fast twist 6-284 & a slow twist 6mmAI...
Both are very fun to shoot & serve their intended purpose well & I'm very happy with both.
Running the 107SMK @ 3300+ in the 6-284
Running 85grainers in the 6mmAI @ 3500+ <<< I love shooting jack rabbits with this combo!
Your standard 6mm with the heavies should offer better BBL Life (properly treated) albeit, at lesser velocity (still nothing to scoff at).
I initially ran the Shehane tracker on my 6-284. Unless running off of a bench, you are going to hate that stock (I did). Hard to handle in the field, sucks on sticks or bipod & generally too bulky for coyote stands...I don't know if the "varmint" model is different or not...
Just my .002