1) Please use Multi Masonry Layout.
2) Do you mean, when you hover stop showing the second image? If so, please use this:
.products .product figure.product-transition-fade .img-wrap.second-image {
display: none!important;
}
.products .product figure.product-transition-fade:hover .img-wrap.first-image>img {
opacity: 1!important;
}
Thanks.