In general, and especially if you don’t know a lot about AR’s, get a gun built by a well known company. The “local guy” is almost never the right option with ARs unless he also happens to be a world class rifle smith.
Defensive use and varmint use are usually on different ends of the spectrum for rifles. On the defensive side, I’d look at something like a BCM.
What is your accuracy standard? “One hole groups” is a little nebulous. A 1 MOA rifle will make a one hole group if you shoot enough ammo at the target. But I assume you’re looking for a 0.5 or 0.25 MOA capable rifle? To get that level of accuracy, you’ll probably have to skew more towards a long range scoped rifle rather than a defensive gun.
Your priorities of light, accurate, and low recoil are all competing against each other a little bit. The AR is already pretty light on recoil, but if you want less recoil the easiest way to do it is to add weight. That usually means a longer and/or heavier barrel. A light gun will usually have a shorter and thinner barrel, but that usually means when the barrel heats up it’ll cause the zero to move a bit (so not as great for accuracy). You can definitely find a happy medium between these depending on your use, but the lightest rifle won’t be the most accurate, and the most accurate won’t be light.
Technique is also a good way to reduce the perceived effect of recoil, so I would place it last on the list as far as requirements. When you get into changing internals and messing with gas systems to lower the recoil impulse, you run the risk of making the rifle less reliable in certain situations. That’s fine for a target rifle, but not so much for a defensive rifle.
Another thing to consider on the defensive side, I know 16” barrels are really popular but an 18” or 20” barrel gives you a better chance of punching through some level III hard armor, especially at close range. In my opinion a 18” barrel isn’t that much more difficult to use indoors unless you’re comparing it to a SBR.
Budget wise, your split will probably depend a bit on your use. For a defensive rifle, I’m a firm believer that you need a sling, red dot (or LPVO, etc) BUIS, and a light. For a basic “buy once, cry once” setup you probably want at least $700-$1,000 in the budget for these. You can find things on sale and stretch the budget, but I wouldn’t expect my Sig Romeo 5 to put up with the same use as my Aimpoint.
