What do you mean off shoulder? Shooting from the hip?
What twist are you looking for ?
almost any twist will work with 5.56 NATO / M855 .
Maybe I missed it but Om not getting a clear idea of what ammo you will be using the most and what type of shooting your doing.
if “ off the shoulder “ means bench then go for the most accurate barrel
If “off the shoulder “ means standing off hand and shooting rapid fire go chrome then?
Standing, leaning, sometimes steadying off random things (hood of truck) versus using a bipod is more technically what I mean by shoulder.