Not sure if you can get 75hz with HDMI.
But you're better off with DisplayPort as 29UM68's Freesync doesn't work via HDMI.
Displayport can be really hard to find anyway.

Watch movie on my X34 are pure joy    no black bar, the slight curve increase immersion also, so can call it homemade IMAX 
Only issue is that it's not easy to find 4K movie ( ehem*pirate*ehem ) coz mostly 1080P that upscale thus not exactly sharp enough. Even found also size damn huge, 46GB 4K Deadpool took 2 full days download.

I think now 4.3K - 4.6K ( found quite good deal in 11street 4.3K with free gifts )

Convert then no point already. Need native 4K resolution video. Most also not in 21:9 format, many still render with black bar in their video 

Yes I am. You can prove me wrong if you want. I don't mind learning from mistakes.