org-ref & helm-bibtex notes

["Julian Burgos" <julian@hafro.is>]

Dear list,

I have been using org-ref for a while, using reftex to insert citations in
my org documents.  Now I am switching to helm-bibtex, which is pretty
awesome.  I have a couple of question about the note files.  Org-ref uses
a single file to keep notes (e.g. notes.org), but helm-bibtex assumes that
notes are kept in separate files, one per article.  My questions are:

a) Do you have a preference in the single file vs multiple files question?
 Are advantages/disadvantages?  I tend to prefer the single file option,
it makes search easy and also I can add TODO items that later I can pull
out in the agenda view.  With multiple files this would not be as easy. 
Do you agree?

b) Helm-bibtex identifies which references have a note file, adding a
symbol on the reference list.  Can we make helm-bibtex look into a single
file (say the "notes.org" file), look for the :Custom_ID: properties of
the entries, and use that to mark the reference list?  I am teaching
myself emacs-lisp but this is above my capacity right now.

Many thanks,

Julian