That sounds like a nice research question!
There was a site I found that listed many of the base oils and how much to use of them and why and what-not, but I haven't been able to find it again. I did find this completely boring, un-designed page that has the same information though: (use Ctrl + - (minus or dash) to make the text smaller if you want to). I learned quite a bit off of pages with this kind of information.
As far as I know (which isn't too much!

) the only reason you would feel oily afterwards would be because of superfatting. I made an all canola oil soap before I realized that was a bad idea... the soap came out SUPER soft, not very bubbly, and overly creamy (as soon as it gets wet it feel like when a bar of soap sits in water for too long). But even that doesn't leave my skin oily afterwards. It actually leaves it feeling quite soft and silky <3

Hope that helps!