There are successfull affiliates using any one of these business models.
Do whatever you are best at is my advice. Outsource the rest to people who excel at the things you suck at.
You will be a lot more productive that way.
One big site or many little ones – I decided on one big one and I am happy. I know many others who have netwerks of smaller ones, and they are happy. It boils down to what you like to do – do you enjoy building and launching new sites, or do you like covering something in depth and build a big site? All of it works.