When desktop resol. is @144Hz with in-game resol. also @144Hz and G-SYNC enabled there is some serious ghosting (only with DisplayPort 1.2 setting). So to fix this just use any other DESKTOP refreshrate except 144Hz when you are gaming (or use DP 1.1 setting). When not gaming desktop resol. @144Hz works good. There is also some barely noticable flickering only on loading screen in BF1. Btw there is no monitor OSD setting for freesync on/off, it runs automatically. To use G-SYNC correctly: 1) Enable it in nvidia control panel, 2) Use in-game high refreshrate resolutions (144Hz), 3) Set in-game fps cap to under 144 FPS (142), 4) Now you can enable v-sync wich won't add any input lag.
* with AOC G2790PX (1080p, 144Hz, TN, FreeSync)