Coyote and longer distance shooting means setting it up as more a predator rifle than a short barreled carbine. Starting with the caliber, 5.56 will do, but you could move to an alternate which won't really cost much more in the way of ammo @500 rounds a year. The issue there is magazine availability - be careful you don't spec yourself into a corner trying to find magazines, and alternate calibers pretty much invalidate using Pmags. Since it's longer range, it also make the .300 BO less than optimal as in supersonic role it's still not a 500 yard gun. For all that - stick to 5.56 and realize that you won't ever find cheap long range or hunting ammo, for some reason the military doesn't want any, so it's all $1 a round like all the other civilian ammo.
That settled, the 20" barrel will deliver more velocity, but a heavy barrel is no guarantee of better accuracy unless you get a high precision one, and that isn't cheap. Just buying a heavy barrel means that's what you got - less machined off the profile. It has nothing to do with actually being better rifled with a precision chamber and a guarantee. A precision rifle isn't made with a no name barrel, it should be listed in the specs as a precision makers by name. It will also raise the cost another $200-300.
Flat top upper gets the scope mounted, a full rail handguard is nearly useless dead weight as you can't bridge the scope mounts onto it. Most scope makers will void the warranty, which should also give you an idea of just how flexible a "free float" handguard really is. It's not wrong to have one, tho - mount the sling to it, and you flex the handguard, not the barrel, keeping the point of aim and impact a ballistic issue of trajectory. Mount a front sight on that rail and you are right back to moving it around, so, don't. It's no longer a free float if you do. Most of the better free floats today do not have rails, they use slots and keyholes to mount pieces of rail and are substantially lighter.
Regardless of all the hype, nearly anybody's upper, lower, and bolt assembly will do. The arguments over testing and being milspec only apply to military issue weapons for the simplest of reasons: It's not milspec unless a government inspector approves and accepts them for government use. Colt doesn't do all that for a civilian rifle unless there's no extra cost and it's no money lost to them - many claim they do, but there's is zero documentation to prove it. They don't even forge their own platters for the uppers and lowers, so "Colt builds them better" should be considered in full light of day.
Fixed stock or not, it doesn't really do much for accuracy despite the price tags attached to the high end ones. I suppose a trained sniper with years of shooting under their elbows could tell, but they could shoot nearly as well without - it's skill factor, not gear.
Same for grip. Lots of styles, not really much in the way of improvement. It's NOT a pistol grip, you rest the weapon on your shoulder and off hand, the grip shouldn't be getting torqued around. It's really a rest for the hand and it's all about pulling the trigger straight back. Trapdoors, swells, whatever, are mostly style, not function for the shooting hand.
Trigger - all the expensive triggers have a travel adjustment screw, which is why they don't have horrible creep over a lot of rough sear. Second, they tend to have lighter pull, but that is a range only user when it's 2 pounds. For traveling across rough country for coyotes, a well made "tactical" trigger in 6 pounds reduces the inadvertent discharge and the coyote won't notice any difference.
If you want to mount a bipod, then the free float handguard would need holes for the rail strip there, most do. A issue front sight isn't necessary, and a low rise gas block would fit fine under a full length handguard. It gets the bipod forward and the assembly has less wiggle for longer distance shooting.
If Brand is important, then pick whatever and pay the premium to have their name engraved on it rather than some other that comes off the same CNC machine. All the lower does is hold a couple of pins, a grip screw, and the magazine, it really has little to do with accuracy - same as the upper. It's all about the barrel, extension, and bolt lockup, so buy the barrel that is guaranteed to be accurate and you will be a lot further ahead than marketing that promises it.
