hello,
> to write documents in plain TeX (no LaTeX) with vim I am looking forward for
> plugins and helpers to do so.
vim comes with those files setting
* syntax highlighting
* format-comments
* [d
* matchit
/usr/share/vim/vim81/syntax/plaintex.vim
/usr/share/vim/vim81/ftplugin/plaintex.vim
/usr/share/vim/vim81/ftplugin/initex.vim
there is also a compiler and an indent file for tex
that can probably be used (at least as source of inspiration).
i would probably start from this and create my own ftplugin/tex.vim
with things like
set aw mp=pdftex\ %
inoremap $$ $$<esc>i
regards,
marc