Some findings on my tests with Nixeus NX-27EDG V1.
UFO tests https://www.testufo.com/ghosting
Running on 144hz low overdrive works with freesync on or off. Other settings do nothing toggling all settings it's easy to see when low setting comes up as it changes sharpness of the moving UFO's.
Running at 60hz there is way to much overshoot (some call reverse ghosting I think). Looking at Simon's tests on the V2 he confirmed that at 60hz the overdrive is more stronger which is what I experienced and is what he found on other monitors overdrive while running freesync. I believe these should be reversed as he suggested, higher overdrive voltages applied at higher refresh rates. Perhaps something that can get fixed with firmware updates unless it can't be fixed for some reason and a limitation of Freresync overdrive but I doubt that.
Gsync pendulum tests.
While running freesync it's obvious again that only low overdrive works on the monitor. What I did find interesting was that if I disabled freesync in Radeon settings I could no longer see any difference when toggling all the overdrive settings on the monitor and the results were all the same. It is obvious with freesync off on the Gsync pendulum demo overdrive does not work, it's most obvious on the test pattern as with overdrive there is a dark shadow behind the pattern and with freesync off none of the settings do this. With freesync on in the pendulum app the pattern is obviously changing when the monitors overdrive is on the low setting as the overdrive is working.
Next I'll try and test some games...
First I tested Battlefield 4 which runs awesome, the overdrive seems great on all settings I couldn't even tell them apart it was definitely working in my opinion. Freesync really works well running on BF4.
Next I tried Battlefield V and freesync doesn't work as smooth as it does on BF4, not sure why but I couldn't even tell the different overdrive settings apart either but it felt like there was more ghosting and I felt more disconnected. I was able to tell when I played firestorm last week while waiting in the lobby that only low overdrive setting seemed to work but I couldn't even get into a game today to try firestorm no players in Australia. Playing BF5 definitely doesn't feel as good as BF4 as the freesync isn't as smooth and there is heaps of juddering something I never see on BF4. Not sure what is going on there.
I think this is a DICE issue with BF5 I am sure from memory even BF1 was smooth though I don't have it installed at the moment so I can't test it. This monitor really shines when playing BF4 feels pretty close to my Benq XL2730Z 1ms Freesync monitor.