I have been promoting CPA offers for over 16 years.
I heavily promote PPL (pay per lead) because there is no credit card / purchase required to complete an offer. All a user has to do is fill out a form to get paid. So conversion rates are typically much higher than offers that require a purchase.
I favor PPL offers that have some form of financial positioning,,,has a make, get or save money angle/benefit. As these have typically performed the best for me.
I also promote free sign-ups (dating for example and free trials +s&h (weight loss, ecig, etc...) I also promote a limited number of offers that are 100% purchases,. With them, I'm usually promoting offers that have some form of financial savings for a popular product, is something that is new unique/novelty or solves a house is on fire type problem.
In the end, it's all about mass appeal. Any offer has to be able to appeal to a vary large audience, so that even with untargeted traffic(at the right cost) can potentially produce good conversions and return a good ROI.
I generate traffic by acquiring data(email). That way I'm building assets that I then own and can market to over and over at low cost. Compared to what most marketers d,o, which is to buy traffic and typically just end up with a bunch of clicks that don't convert well.
Technically, I monetize data and use PPL/free offers to create the path of least resitance to get conversions and convert the data into cash producing assets.