According to this link it would be great to provide 48x48, 72x72 and 92x92. My question, do I need to maintain the same resolution across all different size image? Or different sizes of images with different resolution?
The same link you provided gives you the answer. The resolution should be different for each size :
You should also note that they provided the 48x48 as an example (which works fine for icons) but that the scaling also works for every image you have to use in your application.
An other example would be a 16x16 image (which would be a small contextual icon like a star), you would use the same resolution for each tier, but the size would differ, like so :