Quzzu

The NZXT X62, line most of the AIO's out in the market, are CLOSED Loop liquid coolers.
They are not self-serviceable (e.g. you cannot take them apart and re-fill them).
 
It is normal to hear the sound of "running water" -- experienced the same thing with my NZXT X61.
As @Firewrath9 mentioned, it should go away after a while.

run it straight for 24-48 hours, should get rid of the noises.

Then sadly your issue really is likely to be the GTX 1070 Ti VRM itself... the card is not broken per se however there might not be a way around the whining unless it's EVGA (since they will accept RMA for noticeable whining).

V-Sync eliminates it because its locking the maximum output/performance of the GPU to keep it in line with the monitor's refresh rate. When V-Sync is off, the GPU is unrestrained and can go full bore; depending on the VRMs (and some other factors), coil whine can become quite excessive. 

Ay, I'm an idiot but u're a legend. Huge thanks 

You can also control voltages if you aren't happy with temps.

The H7 is plenty if not a bit overkill for a 8700. 
Unless your temps are too high or the current cooler is too noisy, there's no need to get a new one. 

They are probably overclocking or using the stock cooler. The stock cooler might as well be for display because it is inadequate. For overclocking it certainly can run too hot even if it isn't extreme. At stock it shouldnt be a problem and it will adjust the turbo if it starts to get too hot. 

The Entho Pro M is great for air flow and is pretty quiet when my fans are tuned correctly. Link in sig to see how I have mine setup, although I moved the two 140s to the top (3x140mm top fans)  and put one as an exhaust.
 
The more fans you have the less noise you can have because you're moving more air at lower rpms.

Im a big fan of the CoolerMaster HAF cases (High Air Flow).  With any case to keep it silent you have to control your fans speeds, use fans that meet your dBA and CFM requirements and find a setting for intake and exhaust that leaves your components cool enough to run quietly as well. 
 
I don't see how a Meshify C can be loud unless the end user didn't do anything to keep it quiet.  If I ramp all 11 fans in my Cooler Master HAF (similar to a Meshify C in airflow, they are both considered High Air Flow cases) you can hear this jet engine preparing to take off lol.
 
But with it on my current settings...very quiet.  Enough so I have to be right on it to hear it.  In the room, you only know its on cause LEDs.

I love triple head gaming been doing it for long while, its very hit and miss on games
and sometimes alot of work to get working and there are fixers like wsfixer and flawless widescreen
which I havent needed to use for the longest while
but you will get fisheye effect on many games too
I started with
softh on crts
th2go that was pretty awesome made things easier
eyefintiy once that came out but I always had issues with active adapters
been on nvidia surround since 200/400 series, think I went 460sli and they gave the go surround but added support for my 260sli
I am also sli user too, prolly will be until support drops  from nvidia and 3rd party too
 

Actually, playing FPS games on 21:9 is quite enjoyable, it's when you go up to 32:9 that certain FPS games aren't quite suitable. While 21:9 is fun for just about every game genre out now, 32:9 is great for slower paced FPS, like Strange Brigade/Metro series/Crysis series/CoD/BF series/Doom/etc. For faster paced FPS, like UT3 and the like, not quite so good because too much is going on the screen while you're running around, jumping and shooting.....I'd tried it, and I find it a tad disconcerting. Funny that when I was younger, EyeFinity 3x 1920x1200 monitors didn't bother me, guess I'm getting old.

Go with the ultrawide, it'll be better than 3 1080p monitos stack up, personally speaking if the main purpose is game.
 
Either ways a 1070 Ti is enough yes, but you won't be maxing out settings obviously, going easy on anti-aliasing and adjust settings a little for more balance between performance and eye candy should be enough though.

Go with the Ultrawide, Triple 1080p Monitors are cool but can run into more Unplayable scenarios than the ultrawide. If you're into Sim-Racing go with the Triple Monitor Setup. And if not I would strongly suggest the ultrawide. And your GPU is the perfect match for an ultrawide too.