Still don't get why Panos insists in 90fps because at 90fps without variable refresh rate you'll get either stutter or tearing. Unless you can run your monitor at 90hz without vrr.
On a 144hz monitor (in this case the XL2730Z) anything above 90 you do not feel the lack of Freesync except if you truly focus on the image.
1080 even oced at 2190 cannot cut it. Many games are hovering around 75-80ish with max settings at 2560x1440 (6700K @ 4.9Ghz last year I had it). Is fantastic 1080p card to push 120hz+ but not 2560x1440 or higher.
Yes you can lower the settings, but what is the point? Better stick to the FuryX for less fps but Freesync and max out settings, is better experience. But the FuryX tanks in quite a few games atm, because of the VRAM

Tomb Raider and XCOM 2 are two culprits for me. Also having to do sacrifices on later games like the Division. Especially snow scenes is crippling, or TW Warhammer battles.
For example look at here
@CAT-THE-FIFTH link
http://www.eurogamer.net/articles/digitalfoundry-2017-amd-radeon-rx-vega-56-review
See the 2560x1440 resolution. The FuryX on the 2730Z is better experience than the 1080 in this case. Regardless the higher FPS. On the other hand the 1080Ti you do not feel the lack of Freesync.
I also turning off Freesync on games like World of Tanks with the FuryX. I do not have the annoying flickering of the 2D overlays the game has (chat, minimap), while the FuryX delivers 90-110fps except in some scenes.
I bet you will find people who have experienced the same, will confirm the above.
The 1080 isn't fast enough?
Damn.
For 2560x1440 no, except you have gsync. I mean ok you can game at 70-75fps if you want to, but if you have freesync working atm, makes no sense.
But given the prices of the 1080Ti atm, worth the investment. Even the mighty Aorus Xtreme can be found at £700.
Otherwise wait for AIB Vegas September-October