When I had 4k providing I had the power to run a game at 60fps (90% I couldn't) I found the best mix was to set fps at 59 on a 60hz monitor. Not that it matter's because most games can't get near 50fps in 4k. Plus when you've had more than 60hz you'll never go back. The difference between 60 and 100 is massive, out weighs the 4k sharpness which you forget about within 2 min's of playing a fast paced game.
i did exactly this with overwatch
1440p 144hz vs 4K 60hz
after testing both for an hour each i choose 4K with gsync off [100fps)
if a game dont support it expect strecthed images/black bars on left and right or using a 16:9 resolution or what i had a year ago games crashing.... or not even launchingWhat's the 'hassle' of 21:9?
i love 21:9 but until all dev say 21:9 is a new standard i wont go back for a while (still got one in storage)