btng

From the manual:
 
Which is the "standard retail version" that they talk about here?

Just that Computers aren’t  smart enough to be able to do random things.  Looking random doesn’t mean it is random.

I've had U14S with dual fans blowing bottom to top, GPU on 2nd slot (which is primary PCIe x16). No issues on temp, no touching. Currently it's front to back on same mobo, also no touch nor temp issues. In short, as long as they don't touch, nothing to worry about. Piece of cardboard is enough to remove any issues of touching.

Heat wise no worries then. I wouldn't really worry about a short either, but I guess it's possible, so be careful.

Then there is no big problem with heat but still, @Alex Atkin UK is correct about being carefull not to short anything 

It should be fine, but if you CAN move the GPU down a slot without losing speed then its better to play it safe in case the case gets knock during use.

On the other hand if the GPU has a back plate, there's probably no risk there, only if the heatsink could short circuit components.

I think exhaust, but I'm not sure. I've changed its orientation once after adding fan.
 
The one you buy separately I think. But you can achieve same with speed controls anyway.

Noise doesn't go up so much that you would notice it. Also spinning speed is irrelevant, just use the included pads to have exhaust side bit more away from heatsink. If your mobo has two CPU fan headers, have fan on each. I have it so 2nd only spins up when CPU temp goes over 60C.
 
On mine max temps did drop by 5-7C.

Yeah, that's called a push-pull setup, one fan intakes and the other exhausts, maximum efficiency for heat dissipation since the heatsink is flanked with airflow from both fans. Noise depends on the fans used.
Two fans aren't always needed, however, it's ultimately up to if you want to utilise your cooler to its potential.

Minor things:
 
1. Initial setup required minor calibrating to look really good
 
2. It's an IPS panel so the black depth contrast ratio are good but not the best, if you prefer that over IPS qualities then I think Acer has an ultrawide VA panel as an alternative. 
 
3. One DisplayPort 1.2 and one HDMI 1.4 port might be a problem if you need more, you get only a DP cable in the box. This was actually an issue for me since with my setup the cable was too short and I had to go and buy a longer one. But not everyone has their PC as far from the monitor as I do (actually most people don't).
 
4. If you are really anal about it you can say that the lack of integrated speakers is technically a con
 
Also, I have it mounted on the wall from day 1 so I can't really speak about the quality and ergonomics of the monitor stand.
 
The truth is that this Dell and Acer Predator are the best gaming ultrawides currently on the market and if you need more then you need to wait for those Quantum Dot 200Hz HDR versions that may or may not come in the upcoming months provided you are fine with an expected $2000 price tag.
 
I recommend reading TFT Central's review as they provide by far the most detailed experiences and information about monitors:
 
http://www.tftcentral.co.uk/reviews/dell_alienware_aw3418dw.htm#intro

Here is the thing. The way I understand how it works is the base frequency is 100Hz and 120Hz is OC and thus technically not guaranteed to work flawlessly. Which means there are bound to be some panels that can't reach that without flickering. That being said, AFAIK Dell accepts flickering at 120Hz as ground for return and replacement if it's caused by the panel itself (there are several threads about it here and there, sometimes flickering isn't caused by the panel quality but some kind of software bug). 
 
My Alienware works perfectly fine in 120Hz and I am very happy with it. The only alternative with the same specs is the Acer Predator x34 monitor (the refresh version) and that's because AFAIK it uses the same panel.
 
EDIT: Also, the thing about internet and troubleshooting is that hardly anyone writes that everything is fine. Usually people go and create threads only when they have problems which might give an impression that 90% of monitors are defective.

it does not really matter but a lot of mother boards have a cover over it with thermal tape which will help with temperatures. You probably won't know the difference but it will last longer 

You should always check the manual.
Some may be connected directly to the cpu using 4 pci-e lanes. Some may be connected to the chipset (and the chipset is connected to the cpu through a pci-e x4 link)
 
With this motherboard, most likely all 3 slots are connected to cpu. The CPU has 64 pci-e lanes with 4 reserved for chipset link, and if 4 cards are inserted in pci-e x16 slots they become x16-x8-x16-x8 , so only 48 lanes seem to be wired to the pci-e x16 slots... which leaves me to believe the 12 other lanes would be tied to the m.2 connectors (and third m.2 shares lanes with the U2 connector)
 

Also not all M.2 slots are NVMe, I know you've probably checked but for those visiting this thread from Google and whatnot remember to check

Doesn't matter

If they're all NVMe drives it shouldn't matter which spots they're in

As noted the AC power cord is universal.
 
 On a side note, the internal DC cables are NOT.
The internal cables are all universal on the sata, molex, 24 and 8 and 6 pin output ends
but the PSU side is proprietary, even among makes and sometimes between models.
Which is sooooo inconvenient.

that will be fine, way below 10A.

true, as long as the current isn't over 10A, which it probably won't be unless you have a huge mining rig or something

This was actually brought to my attention recently in a similar post. In no circumstance should you ever use a power cable from another power supply, unless you are most positively sure that each cable plugs into the exactly correct port on both the motherboard and the PSU, unless you want a fried mobo. Basically, the inner workings of a power supply are different for every power supply, so you can never know where exactly the power is coming from and how it is routed to go through the cable, so It's impossible to use another power supply's cables
 
edit: If you're talking about the 3 pin power plug, it probably matters much less, but I'd still use what they gave me for something as important as the PSU

They are the same, so you can use the other one.

Is it the cable that plugs into the wall? In that case, it should be fine, if it meets the requirements for the cable. If it's between the PSU and the PC components, no.

Nope. Just a matter of if it will or wont work physically. 

The listed dimension in this case is the maximum size the retailer guarantees that a component should fit. You MIGHT be able to squeeze in a card thats 316mm or longer (assuming you keep the fan), but it wouldn't be officially supported. For example, I managed to fit a 300mm long GPU (1080ti FTW3) into a Corsair 380T (290mm official GPU length) without modding the case, just moving the front I/O wires.  I've also fit a Enermax ETS-T40 (161.7mm) CPU cooler into a NZXT S340 Elite (161mm) which barely touched the glass. 

Is there a specific case and specific model of graphics card you are looking at? Might help us identify any issues you might have.