Just thinking out loud, but a PC like this will be almost entirely empty space, even with a small microATX case. With no riser cards, you might as well go with a small form factor. Also, you're likely never going to exceed ~150w under any circumstances, so typical 500+ watt PC power supplies are massive overkill.
This small form factor machine needs a CPU, RAM and a hard drive. It will accept any (65w) socket 1151 desktop CPU into it, has two RAM slots (needs laptop sized SO-DIMMs) and will take a total of 4 hard drives, 2 M.2 form factor and 2 2.5".
https://www.newegg.com/Product/Product.aspx?Item=N82E16856158048
Plus, it comes out cheaper than a full sized desktop so you can definitely afford a better CPU.