Overwatch is pretty damn good though.
Yes, but you don't need RAM that fast and probably never will. I have 3000s and don't even run them that fast.
That's really up to you. The speed increase is pretty decent between the two, but at the same time either will be night and day compared to your old i7.
Depends on which board you get.
Again up to you. There are several ways to hide unused cables or you can go convenience.
No, 16GB is fine I was just talking about the speed. The RAM you linked is perfectly fine, but if you experience any crashes using the XMP profile then you'll need to be able to manually decrease the RAM speed.
You can get either of the 3 chipsets in mATX or mITX (smaller than mATX) with all features from Z170 to H170 to H110. The feature differences are in the chipset, not the form factor (size). Get what suits what features you need. Always remember (for 2016 that is) that USB2 ports aren't really needed beyond 2 (mouse and keyboard support for Windows 7 IF needed) and that a USB3 port handles well with a hub. All of my devices on my machine actually run off a USB 3.1 Gen 2 port. That includes 2 external SSDs, mouse/KB, Xbox One wireless adapter, CronuxMAX+, joystick, and Oculus Rift.
Any size you want that fits an mATX board lol. With a smaller than 10.5" graphics card what can be used is greatly increased in terms of smallness. It's pretty personal preference, so if you really want me to help go ahead and link a few you like and I'll give my opinion on them.
Honestly, if you for real won't be hardcore gaming ever a quality 500 or 550W PSU is all you need. Here are some of my choices in no particular order.
Just a designation for factory overclock. The only cards that make a difference with them are FTW, Classified, Kingpin, and Hydrocopper editions. They sell the different versions for marketing purposes, like how you were questioning the 20 dollar difference between the 6400 and 6500 in hopes of people saying "Oh 10-20 bucks for slightly higher clocks isn't bad" when the manufacturing costs for each card is the same until the FTW edition. I would just get the cheapest which should be the smaller looking one.
