I exactly have same problem.
7700k @4.6ghz, gtx 1080, 8x2gb 3200mhz ram, the game and windows is installed on ssd.
My monitor is 1080p,@144hz. I am more than sure my rig can handle more than 72fps but it is almost at 72fps all the time with every settings.(common,cursed,rare,myhtical etc.)
---V-sync and FPS cap off in every situation---
Whenever i choose windowed mode instead of fullscreen, my fps increases to the level that it must be.(110-144fps)
Also whenever i choose other resolutions (900,720,540p) there is no problem about fps. Everything seems normal
I have no problem on PUBG,Battlefield1, GTA V and CS GO. I think problem is not my rig, something is capping my fps in this game. I would like to get some help if anyone had and solved this problem. Thanks a lot.