There are 2 options connected to right margin:
Editor -> Appearance -> Show right margin
Code style -> General -> Right margin (columns)
However you can set only one value for right margin.
According to PSR-2 ( at https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md ) :
There MUST NOT be a hard limit on line length; the soft limit MUST be 120 characters; lines SHOULD be 80 characters or less.
It would be nice if you can set 2 right margin values and display 2 lines - I would like to set 80 and 120 characters and display those 2 lines but at the moment it's not possible (I believe).