Vim is my day to day editor: I use it for coding and writing prose. Vim was made for programmers, not really for writers. Here are a few plugins I use when I write prose with Vim.

1. Goyo offers distraction free mode for Vim. It lets me to resize the writing surface in the editor’s window however I want.

2. I like soft line wraps when I write prose. Soft line wrap is when the text reaches the end of the window it gets wrap back to the beginning of the next line without inserting a new-line. Vim Pencil lets you do that.

3. vim-textobj-quote offers support for smart quoting as you type like Unicycle but this plugin is still maintained.

I have this snippet in my .vimrc to get in and out of the writer mode:

" I use a 80 columns wide editing window
function s:WriteOn()
    call pencil#init({'wrap': 'soft', 'textwidth': 80})
    Educate
    Goyo 80x100%
endfunction

function s:WriteOff()
    NoPencil
    NoEducate
    Goyo!
endfunction

command WriteOn call s:WriteOn()
command WriteOff call s:WriteOff()