I finally caved after keeping an eye on them for a while - particularly pricing. I still think the increase for a g-sync ultrawide is insane but I'm glad I waited to go that route.
I went with AOC's 35" AGON VA, which has been great so far. I ended up having to swap DP cables as my old one prevented g-sync (and 100hz) from working properly for some reason. And I also had to switch my speakers to the monitor output jack, as I ended up getting a bunch of interference from onboard after switching monitors. I have heard there are some issues when video cards are under load, but I never had it before.
Most games I've tried so far support 21:9 and support it well - Witcher 3, ESO, Lego Worlds, Destiny 2, Subnautica, KF2. I wish No Man's Sky didn't have the stretched HUD as it would look great otherwise.
One of the Asus IPS panels would have been nice too but they were also ~$400CDN more and the thing wasn't cheap as is. Even ignoring the size difference I already notice a huge improvement with g-sync as well as with colours and blacks in general. I had a BenQ XL2420Z before so it is a drop from 144hz to 100hz, but I found myself setting it to 100 or 120hz already and the lack of tearing AND no input lag via v-sync is well worth it. Plus, my 1070 wouldn't be able to push many games over 100fps at 3440x1440 anyway.
Main downside? My left monitor, which doubles for my PS4 and Xbox One, now looks tiny.