The artifacting icons can't be helped due to the icon's original small size. When set to be viewed any larger than their original size, they will artifact like that.
Personally, I do not see a difference between the icon sizes in your screenshots. They look the same to me other than one in "Tiles" and the other "Medium icons". Both have medium icons by default.
The only way to change that is to use the scroll wheel method to have a custom size. Of course, this is not going to help with the artifacting for the above reasons.