We are in the same boat. After years of owning nothing but bolt guns, I recently bought an AR15, and have now added an AR10, obviously I like it! I spent years reloading for precision accuracy (benchrest), so reloading for the AR rifles is certainly different. Higher volume precludes all the case prep crap (except for timming, which is almost always needed with the .223 after the first firing), and it's not necessary anyway, not for the kind of shooting I do with it. Given the time involved, even using a Dillon progressive press, reloading for the .223 is probably not worth it; not with decent ammo available at $3.50 a box, and some questionable stuff even cheaper. In answer to your questions, yes, you can get more accuracy from your rifle by finding the right handload, but again, the difference isn't worth it to me. I do virtually all my AR shooting inside 100 yards, mostly plinking targets. And no, you should not neck size only, since the cases will get too tight for total reliability.
I will definitely reload for the .308. I have just loaded some surplus, pulled 147 grain bullets in surplus primed brass, using surplus wc846 powder, and my all-in cost is about 17 cents; cheaper than top grade .22 rimfire ammo! This AR stuff is great! I shoot more now in an hour than I shot my bench guns in a month, plus the targets blow up, break, or roll around!