Hello Pisces -
I am sorry to hear you are encountering difficulty with Preview. We are not aware of any issues that would cause images to supersize to an unexpected size, they are expected to show larger in the popup than they do on the listings. This does not mean that the images would necessarily show at the size you uploaded them at, the supersize function should display the images at an optimal large size for the screen they are being viewed on.
Unfortunately, there are no specific controls within your account that would affect the size of the supersize images within your listings.
If you find that the images are supersizing to a size that is larger than your screen and you have not adjusted the standard browser zoom settings to be zoomed in, please let us know a few examples in your account where this occurs in a support case and we'll be happy to look into this for you.