I feel like I have to update my post after my further experience with the same model because I found it unfair for the potential buyers.
So after I successfully returned my first kfa2 gtx 1070 ex I decided to give it another try. I was lucky to find two good offers within a sort period so I bought them both (lol). So I had to decide which one to send back and which one to keep after some testing
And now to my impressions. One model had its back plate screws loose again and the other not at all. I simply screw them a bit just enough so they were not loose.
Now after I installed them both to my system I did some stress tests and this time the results were good. The temperatures were much better than my first gpu so I guess it was faulty.
Even at the Witcher 3, where previously it was struggling to stay under 80 C with 100% fan speed and oc @ ~2,050Mhz now both stayed ~65 C. In Firestrike test they both showed a good oc performance with ~2.075-2.100 MHz.
Both have Micron GDDR5 chips and after I flashed them both with the vram bios update they work fine. One of them though oc better than the other with ~2340MHz vs 2200MHz.
I later realize that you can flash with KFA2 GTX 1070 EXOC bios so you can have better core stock speeds. I tried and it is now a EXOC model. There is of course a fan stop option also.
The bad ones:
Both of them have coil whine. One of them though had a bit less coil whine than the other. I am not sure if this is a coincidence but, the one with more coil whine was able to squeeze a bit more overclocking. I read that coil whine is hit or miss so who knows. It can be annoying to some people but I use headphones.
Overall it is very solid and nice buy for a great price.