Your PCpartpicker list isn't like-for-like though.
Don't get me wrong, the Asrock M8 gaming PC is a pretty decent deal at $200 instead of $550, the case alone looks to be a very high-quality item, probably worth at least $100 by itself. I'm in two minds as to whether you should or shouldn't but the fact it's an outdated socket type makes me swing towards the "no" vote.
The PSU is also decent, which is rare in a barebones but I guess Asrock were originally asking $550 for this so they're not going to skimp on PSU.
As for the board, it's a pretty low rent board with a very odd configuration; Laptop SoDIMMs are a major turnoff, because that means expensive RAM and none of the high-bandwidth stuff you can get in a normal desktop DIMM format. It's also low on power delivery, with the bare minimum number of phases for the CPU. You might be able to overclock on this board, but barely as 3-phase is bad and the VRMs aren't even cooled. If you're not overclocking why pay extra for a Z-series chipset? Anyway - identity crisis continues with a total of six SATA ports in a case that has room for just two drives.... Let me put it this way - the board isn't terrible, it will work just fine - but if you could choose your board from a list of outdated Haswell boards, it would still probably be right at the bottom of any sensible list.
Lastly, don't forget that the CPU cooler requirements for this form factor are going to be pretty demanding. Some of the "cube" style mITX cases will take 92mm tower coolers but you're going to need to pay a premium for something very low-profile if you want quiet cooling or an overclock with this M8 barebones.
How's this for a build? - PCPartpicker doesn't have the RVZ01-E but that lets you ditch the optical drive in favour of a better value and quieter ATX PSU rather than putting up with an SFX one. If you really want the optical drive in a SFF you probably want to ask yourself if you wouldn't rather be building an mATX gaming HTPC using something like
this.