So I'm building my first PC

Gonna need a Titan X to run those above 20 fps 

Look at Overclockers UK, they can be pricey, but all their prebuilts come with configuration options, so all the parts will work with each other and they stress test your system until it's ready, I've had my PC for over 4 years now from them and it's worked flawlessly 

I'm only going to use this build for a couple of months, I built all this just to get a feel for everything so if I mess something up it isn't going to be that big of a deal I plan on upgrading to a ryzen 5, 1050 system later this year

Pretty good deal in my opinion. Well done on going to the effort too. My son could probably take a leaf out of your book when it comes to building computers but it's always to hard for him trying to work it out when stuff doesn't work and he just doesn't want to pay attention when I try and work through it with him. 
I know I shouldn't give him the easy way out since there's so many computer bits in the home which he can turn into a basic gaming computer including a 3GB Radeon HD 7970

I know i shouldn't since he needs to learn to put the effort in and discipline himself to do what you are doing but I caved and bought him a premade Dell which came with a Ryzen 1700 x and RX580 with 8GB VRAM.  

You didn't mention, Motherboard, Operating System, Chassis,PSU, Monitor or keyboard/mouse. You will need those though and you probably have them already. 

For clarification, the 16GB DDR3 you mention is RAM and not VRAM(video RAM), while the 2GB mentioned next to the r9 270X is VRAM.

Game suggestions - This Page should provide you with some insight into how the card should perform in various video games. It doesn't look like the R9 270X has been benchmarked specifically but it's ranked 105.

Although, I don't know  much about WoWs and ultra requirements and my gut says no due to Vram limitations, The folks at notebook check have some Information which suggests it quite possibly might, at least with the 2015 version of WoWs that they tested.  The graphics engine used by the 2015 version of WoWs was very conservative.

The R9 270X is ranked 105 in terms of performance across all video cards and while it wasn't measured specifically, cards ranked lower seem to cope with Ultra settings.  The setting they refer to as Ultra are

The 2GB VRAM may still be a bottleneck though and depending on whether the graphics engine has changed and new settings are now inclusive.

Ultimately the only way to be sure is to try it out. 

i'm not too au fait with gaming cards these days but I would think you'd be hard pressed to find a 16GB video card for gaming. I'm not sure if there is a 16GB version of the Titan X though. There are those Nvidia Tesla V100 and P100 which are around 10 grand and have 16 or 32 gigabytes but I don't think you can connect a display directly to them. They are pretty much purely used for number crunching as far as I know.
I don't even know how much CPU performance limits high performance GPUs performance but it likely will to some degree. I take your point though. If money was know object.....

You have 16 gigabytes of RAM, so 64-bit Windows 10 would be perfect.

Windows 7 and Windows 8.1 while they were alright at the time, are not getting outphased and with that comes a huge risk of security vulnerabilities 

For gaming in 2019, Windows 10 Home will suit most individuals.