A good question and the answers don't have to get too complicated. Lots of folks want to recommend short barrels for 300 BLK but that really applies to subsonic rounds + a can. Any supersonic loads you shoot will not be adequately burned by such a short barrel and you leave a lot of performance behind. If you want to shoot at 100 yards and possibly hunt, that 16" barrel is going to be best. Not only for the full velocity you will extract from the loads but the longer sight radius helps a lot for accuracy.
You linked to a good company for your barrel info, Ballistic Advantage. I highly recommend them and their 16" 300 BLK barrel is a top shelf option at a very reasonable price. The QPQ finish is same as Melonite which is very corrosion resistant. My oldest AR has a Melonite barrel and it has held up perfectly through the years despite being my range rat gun. The standard 1/7 twist is good for the typical range of 300 BLK rounds, from subsonic to supersonic. Until you use a can, I recommend 125 grain supersonic loads.
16
If you just want to buy a complete upper, the 16" Aero 300 BLK uppers will have this barrel in them. Aero bought out Ballistic Advantage and mostly if not exclusively uses BA barrels. Pretty sure the same guy runs BA, he just partnered with Aero.