If you absolutely have to have a milled AK, get an Arsenal SLR-101S. The SLR-101S carbines that I have seen have very good alignment of the barrel, gas block, and front sight. The bolt carriers move smoothly on the receiver rails. The guns come with a side rail for mounting optics. The receiver is hot hammer forged and the barrel is cold hammer forged. The stocks are quality US made polymer. Hard to ask for too much more for 1K.
There is no advantage to milled versus stamped AK's. The AK-47 was originally designed to use stamped sheet metal receivers and the very first guns did have stamped sheet metal receivers. The Russians did not have sufficiently precise welding technology at the time they were manufacturing the original AK-47's, so they decided to mill the AK receivers from blocks of steel because they had the machinery available and the machinsts were familiar with the machining processes. When the welding technology became available, they switched back to stamped receivers.
The milled AK's heavier receiver shifts the balance of the weapon more near to your fire control hand. The stamped AK's lighter receiver shifts the balance of the weapon more near to your support hand. The milled receiver AK's weigh a bit more than the stamped receiver AK's. If you don't like weight, you won't like a milled AK. There are also things you can do to a stamped AK to make the balance pretty close to a milled AK.
There's very little difference in accuracy between a properly manufactured milled or stamped AK. Spend your money once for a quality product and then spend the rest of your money on ammo.
A milled AK's receiver can crack with a lot of use. A stamped AK's receiver can have sheared rivets with a lot of use. The amount of ammo required to destroy any quality AK will pay for enough AK's to arm a squad of men. Very few people will shoot their AK enough to wear it out. If you buy an AK, do yourself a favor and wear it out. Then go buy another one. All machines can and do break and no carbine or rifle that I am aware of has an infinite service life. That said, the service life of a quality AK, stamped or milled, is pretty darn good.
United States Code Section 922R compliance means you need to have a certain count of US made parts for your foreign made carbine or rifle to be considered US made. Go read what the law says and then ask questions about it. If you can't find the law or read what it states, perhaps it's best if you don't buy a foreign made AK.
There's nothing special about Polytech or NORINCO AK's except that the Chinese used 1.6MM stamped receivers in the stamped guns and heavier barrels in all of their guns. Fit and finish of military weapons was never a real priority. What matters with respect to military guns is that they meet the specifications set forth by the military. All Chinese AK's that I've owned or handled had average finish, loose tolerances, smooth movement of reciprocating parts, and good but not great alignment of all the critical parts. Polytech AK's are generally of slightly higher quality than NORINCO AK's, but NORINCO AK's go bang when you pull the trigger just like the Polytech AK's.
Any properly built new manufacture milled or stamped AK is going to be made with modern materials, technology, and quality control. If you just want a milled AK because you want a milled AK, there's nothing wrong with that. Apart from that, the accuracy and durability of a properly manufactured stamped AK is equivalent to a milled AK.
My suggested brand of quality milled AK to purchase is just that. A quality made product from any manufacturer is just as good and Arsenal sometimes makes mistakes just like all other manufacturers. The brand and type of product you choose are best left for you to decide.