Emacs (which I did try for a while) certainly has the flexibility, but is very "opinionated," like most text editors, it seems.
Curious to see if this question makes sense to folks?
https://micro-editor.github.io/
Like OpenBox, most casual users can be dropped in and know their way around their interfaces, and both options are kinda lightweight compared to other modern options. There is power available for serious customization if you want (you can write plugins for them in Python and Lua, respectively).
Personally, both Vim and Emacs do not remind me much of OpenBox. I think i3wm is more a Vim, and I guess XMonad is the most Emacs-like window manager I've tried. (Arguably, EXWM is the only truly Emacs-like window manager...)
1) openbox is a gui window manager. When run from a text console, a gui window manager provides access to graphical environment. ( additional example: Solaris NeWS window manger[10] )
xinit[9] is one aproach a user can use to customized which window manager to start/use.
tmux[1], screen[2], byobu[3], wezterm[4] provide console 'text' equivalents (aka no graphics/graphics drivers) of gui window mangers such as openbox.
3) text editor with 'run-time' presentation extension of protocols such as html : vim live server[7]
4) write one's own custom interface to use with bashed[8]
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[0] : intro to terminal multiplexers (part 1) : https://www.youtube.com/watch?v=R0upAE692fY
[1] : http://github.com/tmux/tmux/wiki
[2] : http://www.gnu.org/software/screen/
[3] : http://www.byobu.org/
[4] : http://wezfurlong.org/wezterm/
[5] : http://en.wikipedia.org/wiki/Leafpad
[6] : http://github.com/overleaf/overleaf
[7] : http://github.com/wolandark/vim-live-server
[8] : bashed : http://github.com/justinyaodu/bashed