I've been using olivetti-mode for a little while when I write notes in org-mode and I must say that I really enjoy it. It seems like a very simple package. It doesn't have very many interactive functions or customizable options. Essentially it comes down to you enable it and you pick the default width of the text that you want. The initial 70 is a bit too small for me, but 80 or 85 is pretty comfy.
It's also possible to have it enable and disable
visual-line-mode. Personally I always have this on in Org, ever since I started using