Welcome to the site!
You will find a wealth of info here on the 338 Edge. Dont be shy of the search function. ;)
Most guys here using the Edge are running 28-30" of barrel which most of those are running 30" A few are at 26" IMO, 28" is minimum and 30 would be better. (I am running 28" 10x)
A 10x will stabilize any of the mainstream 300 grain bullets such as the SMK, Berger, Scenar etc....with room to spare. 10x is very poular. Some guys use 9.3 for the 300 grain pills. If you ever want to run some ofthe heavy mono metal bullets you may need a 9 or 9.3 but of you stick to the readily available 300 grainers or lighter, 10x will do just fine.