I used several nofollow plugin and this one did always the job.
Regarding what was said in a previous comment, this plugin logically detects external a href links. It does not detect iframe and script. This is what is expected because googlebot isn't interested in iframe and script.
So, it is possible to put a nofollow on affiliate links case by case.
On the other hand, i have used "WP nofollow post" and i faced issues that were not acceptable. For instance, once on one update WP nofollow post generated a 500 error on every single page with a link. WP nofollow post also missed some links and i still don't know why today. However, a nofollow plugin is very important today because of google penalty.
So it has to work.
Only downside of outbound links manager, we cannot change the number of displayed links on one page, so when we have many links we have to go through every page and it takes a long time.