I'm using emacs 25.1.1 with the prelude config. In Atom I used to have a setting that made my lines wrap at 80 characters (without cutting words) for better readability. I've searched on the web for something similar for emacs but I have not found anything. Any ideas on how to do this?
auto-fill-mode is what you're looking for. You can enable it automatically for editing text by adding this to your config:
(add-hook 'text-mode-hook 'auto-fill-mode)
You can customize how long lines in your text documents should be by customizing the
fill-column variable. For example:
(setq-default fill-column 80)
If you want to to make sure that lines don't split on your screen as you're typing things, you can set up visual line mode.