If you are after traffic, you need to concentrate on traffic research and linking articles as much as the actual writing. When you have an idea, go to Adsense Keyword Tool and type in related phrases and it will tell you how many people are searching for those phrases each month. I usually go for a phrase with at least 3000 searches a month. Then, type that phrase into Google search and see if anyone else has written an article on that phrase. If there isn't much competition, write the article and use the phrase in your title. Another important tip is to link your related articles. I write on a niche subject and at the bottom of each article write a list of all my related articles that I think the reader may be interested in. I get a large percentage of my traffic this way.
Re quantity, you can write and publish as as much as you want, but why waste your time writing articles that no-one wants to read, that doesn't get much traffic. It is better to write a good quality hub on a subject that gets a lot of searches a month that no-one else is writing about. Also do you know about the Pareto Principle? The 80/20 principle? It works on hub pages, I find that 70-80% of my traffic comes from 20-30% of my hubs. Take a look at your own hubs, you will probably find this is true for you too. Analyse those top 20% hubs. Why do you think they get traffic? I know why my top 20% do. They are good quality, written within a niche that I know about and am interested in, where there is only a handful of competition from other writers, ,they contain original photos that I took, (that end up on sites such as Pinterest, which draws in traffic), and also YouTube clips that make it extra interesting for the reader. So Hubpages was right all along - write good quality Hubs and make them interesting for the reader with relevant extras such as photos, links, YouTube clips etc..... Happy writing :)