Kanade
So the first method 1. framedoubling (frame interpolating) to 48 fps and then frameblending to 60 fps. is the one you explained before?
Yes. Framedoubling + frameblending can be implemented by two ways: via SVP only and with blending in madVR.
using either of these method will result in artifactless?
Yes.
frame interpolating to 60 fps, how do you do that?
it is default frame interpolation way.
Target frame rate: To screen refresh rate (default).
24 * (5:2) = 60.
And how do you achieve smoothness and sharpness?
Sorry. I can't understand what you want to know? Theory from start to end? It is impossible in one forum post.
I'm still confused on the two methods you have explained as well as three effects
Read again. 
Try it on your video. You will see the difference.
You will be surprised these two are not all methods 
Third one is use interpolation only without blending but turn display to multiply framerate: 48 Hz or 72 Hz.