For an inexpensive lightweight setup that'll set yourself up for proper eye relief I'd go with an aero precision mount. Some guys say they are weak at the hinge but the 3 or 4 I've had have been yardsailes off trucks, down hills, bounced on 4 wheelers and not treated nicely and havent had an issue
The adm 20 moa rail is the cats ass. Mine would reattach within 1/2moa every time. Bit heavier and a bit more money.
Not sold on larues qd locking system. Supposedly chews rails.
The 4-16 hst is pretty weak sauce up into the 13-16x range so plan accordingly.
I've got tons of Larue and ADM mounts, been using both for years, they seem to work equally well.
You can use a SFP scope but remember the ranging elements in the reticle will only work at one magnification. You don't need more than 10x to get to 1,000 yards. I'd get a more expensive lower powered scope so you'll have good resolution at those distances. Good glass at medium magnification beats mid-range glass at high magnification.
Warne one piece cantilever mounts are pretty damn good for the price. QD style are over kill for most folks, get one if you need to remove the scope cause the combo wont fit into a hard case or will be screwing around moving it to other AR's. The cantilever aspect doesn't need to be the extended cantilever style, but it'll allow you to mount to the upper receiver picatinny rail only and not have to bridge onto the hand guard; and therefor you'll get the eye relief needed. You can typically get away with rings (AR High/1.5" high) on large frame AR's due to the amount of pic rail available and still get the proper eye relief, if that makes sense. Good luck, the Grendel is a lot of fun to train for distance shooting. Matt in CdA