"Primarily for hunting", "for defense", and "love shooting them" don't all necessarily go together well. The .308 AR you buy to hunt with is overly powerful for defense unless you live out in the sticks or your neighbors don't mind the possibility of bullets coming through their kids' bedroom walls should excitement happen at your house. And to top it all off, .308 isn't the cheapest thing to love to shoot anymore, either - 5.56 is somewhat more available, but not at all suitable for game larger than deer.
From what you describe, I'd stick with a 20" .308 rifle. Stocks aren't a matter of a simple "swap" (you'll need tools, different parts, and some familiarity with the platform), so stick with a fixed version. I'll be the "fudd" and tell you to save the money you'd have spent on a cool-looking but otherwise only marginally useful vertical grip and put it into quality optics or rings instead.