When I last wrote about this, there were two really good options for what I was looking for. Now there's only one, as Static CMS has been discontinued.
I'm bummed out about this, because Static CMS continued to have the better overall interface, and while I've tamed the Decap CMS interface a bit via the kind of thing you find when you dig through the issue queue, it's still not quite as good. Which, again, is a bummer.
But! Not the end of the world. I'm using Decap over on another blog of mine that I've been starting up recently, and it does work. I do wish the mobile interface kicked more butt, even with the hack styles implemented; it does seem like there's active work on the UI going on now, which is great. I'm holding on to see what's coming.