Backlinks help SEO. Simple as that.
Moreover, if you are posting in forums relevant to your niche, there is a good chance that someone will click your signature link thus increase your traffic.
Backlink is one of the most important factors in Google ranking. However, remember to have ORGANIC backlinks through RELEVANT sites. Google does not tolerate foul play.
I would assume you are referring to Submit URL.
I always submit URL after finishing a blog post. It ensures the index of my URL and as you know, no indexing means no one can find it through search engine.
By face to face do you mean meeting with a person in the real world?
If so then I would assume you are refering to direct marketing. Direct marketing ensures a better conversion rates due to trust factors etc. However social media ensures outreach to a large number of people. In my opinion...
As a person who is specialized in SEO, I would sugget researching keywords related to your niche. When you find a good one, create and optimize your Facebook Fanpage accordingly. Fanpage can rank in Google as a normal website as long as you put effort into it.
Bounce rate tends to be a big problem nowadays, considering people have little time and can easily click back. For me, I often create internal links to decrease bounce rate.