Multiple Channels vs Playlists on YouTube
Generally, you are much better having one channel and placing all your videos into this single channel, with different playlists targeting the different audiences.

However, I'm assuming the videos are somewhat related. If they are on completely different topics (for example Gardening and Software Programming) you may find that it's better to separate so the subscribers don't get overwhelmed by videos in the wrong category.

If perhaps you have a brand, say a magazine (Home World, for example) and you have separate categories (Home World: Gardening and Home World: Decorating) I'd say stick to a single channel for branding purposes.

And to answer your final question, no, generally YouTube will treat separate accounts as separate entities for the purpose of monetization.