ATX/mATX builds have always been relatively straightforward and easy to build, with ample room and great cooling at the expense of a lot of wasted space. This time, I went with the NCASE M1, which has extremely favorable reviews on both HardForum and r/sffpc. Hopefully this helps prospective builders out there.
i7-7700k - Out of all things, this is probably the only piece I would've swapped out. I do a variety of work besides gaming, which Ryzen would have a slight edge in. Losing ~10% or so average FPS in favor of improved performance for multimedia work seems like a good trade-off. Delidding is something to consider, especially if you overclock. Mine was able to hit 5.0GHz with 50x @ 1.376V and 72°C, which was quite impressive considering reports of temperatures in the 80-90°C range without delidding. A shout out to Silicon Lottery for their service here.
Noctua NH-C14 - Incredibly difficult to source one of these, but it's the premier air cooler for NCASE M1 builds. It is 99.9% a perfect fit for the case, as the NH-C14S is ever slightly too big and would require slim fans on the side panel in order to fit. They show up on eBay once every 6 months or so if you're patient. That's how long it took to get one. Otherwise, consider other options.
Asus Z270i - One of the only mini-ITX boards out there with two M.2 slots, plus a BIOS I'm already familiar with. Nothing much to say here, they're all pretty much the same. Do note that the M.2 slot underneath the M.2 heatsink (front, below processor) is the only one that supports SATA as well as NVMe. The one on the back only supports NVMe. If you opt for a SATA M.2 drive, put it in the front.
G.Skill TridentZ 2x16GB - This set was DDR4 3200, Timing 14-14-14-34, Cas Latency 14, and is only necessary for trying to max out your FPS to feed your ego. Also overclockable. Otherwise... yes, it's fast RAM, and hardly necessary for gaming. I've never been too obsessed with color scheme matching, but it matches the board well.
Samsung 960 Pro (NVMe) and 850 EVO - The 960 Pro is ridiculously fast. You also will probably never see any real world benefits from this thing under normal use cases. I haven't actually gotten around to benchmarking it, but games load quite quickly. Might be a placebo effect. The 850 EVO is used primarily as a drive to store downloads and temporarily cache Shadowplay recordings. SSDs do have a long lifespan, but the constant write/rewrites from Shadowplay make me lean toward wearing out a cheap drive instead of an expensive one.
EVGA 1080 Ti - Hot and noisy, but that's sort of what you expect with blower cards. Initially I tried a 1080 FTW2, but I didn't really like dumping all that hot air back into the case in such a small chassis. The 1080 Ti came out soon after, so I upgraded to that. Basically, the tradeoff is basically a warmer card vs. a warmer everything else. I had a few spare 90° adapters from a previous build for a friend, and would definitely recommend buying two if you don't have them.
Corsair SF 600W - One of the few SFX PSU options. General consensus favors Corsair over SilverStone. 600W for extra headroom since I want to keep CPU/RAM overclocking options available, plus the 1080 Ti is a hungry beast that draws a fair share of power. You can probably get by with a 450W, but 600W is marginally more expensive and provides a comforting amount of leeway. If you're already doing a 7700k+1080Ti build, I feel like you might as well spend the extra money to have some breathing room.
Windows 10 - It's still possible to do W7 to W10. Installing W7 on Kaby Lake is a pain, but it's possible. You need to sideload the USB3 drivers, which can be done with Asus's EZ-Installer. You'll also get the "Windows setup could not configure to run on this computer's hardware." error. This can be resolved with the following:
It'll still appear to fail and will loop back to the failure to configure screen. You can ignore that, hit cancel, and proceed further with no issues. If you run the command prompt sequence again, you'll end up with two user accounts, and so on.
be quiet! fans - Quietest non-beige/brown fans I could find. I like Noctua, and even though I'll rarely see the fans, having dubiously colored fans still sort of bothers me. Otherwise I would've run with a set of Noctuas. The intake fans below the GPU have marginal benefit and do add noise, but since the case is set up to have passive exhaust, it's helpful to get as much cool air into the case as possible. I do confess that my knowledge here is a bit spotty and probably requires more reading. If you want to run 5 fans, you'll need some Y-cables, as the Z270i only has 3 PWM headers. A small unintended benefit to having fans below the GPU is that the GPU doesn't sag.
CableMod cables - With space at a premium in this case, having less room taken up by cabling is definitely a plus. You can use the following lengths as reference. The EPS/PCI-E cables are ever so slightly longer than I'd like, but I erred on the side of caution. Do note that at the time of purchase, the Asus Z270i offered a discount code for CableMod cables.
24 Pin ATX - 250 mm
4+4 (or 8) EPS - 400 mm
6+2 (or 8) PCI-E - 150 mm (2x)
If you want to run a SATA drive (mounting where the ODD would be), 100 mm will be what you're looking for.
Hope this helps future builders. I am also a dreadful photographer. Sorry about that.