I have been trying to get Org Mode to work with a variable-pitch font, when I stumbled across the videos and website of Protesilaos Stavrou. Amongst all the 'gold' I found there, was the themes he has developed, Modus Operandi and Modus Vivendi. The first is a light coloured theme, whereas the other is a dark theme. I've been using a dark theme for a long time (I don't know how long), but the elegance of his themes had me switching, first to Modus Vivendi, and then to Modus Operandi. It's rather nice.

I also managed to fix (mostly) using a variable-pitched font (good old Verdana — don't hate me for trying it). To do that I use the org-variable-pitch package from Göktuğ Kayaalp (which is available via MELPA). Yes, I could use many other fonts (FiraGo, Hack, ETBembo, and so on), but I went with what was to hand (bricolage at work).

(set-frame-font "Consolas 11" nil t)

(set-face-attribute 'default nil :family "Consolas" :height 110)
(set-face-attribute 'fixed-pitch nil :family "Consolas" :height 110)
(set-face-attribute 'variable-pitch nil :family "Verdana"  :height 110)

(set-face-attribute 'bold nil :weight 'semibold)

(require 'org-variable-pitch)
(set-face-attribute 'org-variable-pitch-fixed-face nil
      :family "Consolas")
(add-hook 'org-mode-hook 'org-variable-pitch--enable)

Now I am working on getting Olivetti Mode work well, so I can have a pretty writing environment.