Disable image zoom on selected attributes and thumbnail image quality

Hi,

1. I disabled product image zoom on my product page.
However, when I select the color, the product image changes,
and the image can be zoomed again when hover. (I don’t want zoom)

2. On product list page, product image changes to variation image when I select color attribute.
But the quality of variation image looks lower than product image. It looks blur.
I’ve tried to adjust image attribute size, but it doesn’t help.