If you think that real people might see those links and click on them then yes, they have a value. Otherwise, no.
For example – signature links here on SPF. If your site is vaguely relevant to people working in internet-related fields and you have built a reputation as someone who is worth listening to, you might well get some traffic through your signature links. On the other hand, if you only post vague and empty waffle occasionally, and your site is completely unrelated to web design, you're unlikely to get anyone clicking through at all.
Utter, utter rubbish. Anyone who thinks they can second-guess Google's algorithm and thinks they are smart enough to work out a ratio of nofollow to normal links that is some special magic number that Google will approve of is seriously deluding themselves. The reason for getting nofollow links is if they might help you get direct traffic. They will do you absolutely no good whatsoever in terms of SEO.
More to the point, having any nofollow links is a clear indication to Google that you have almost certainly been link-building yourself, which is precisely what they don't want. They couldn't give a wet slap how many links to your own site you have seeded, because that tells them absolutely nothing about the quality or reputation of your site. They are only interested in what other people are saying, and those links are far less likely to be marked as nofollow. We've seen some pretty crazy ideas for SEO over the years but deliberately building links that Google is going to pay no attention to and that are going to do your link profile more harm than good has to be right out there.