I would like to change the fixed height from 460px to a height that covers the whole popup. I have found the following CSS to be working, but do you have another suggestion?

Input the following in your Themes custom CSS:

.woosq-popup {
    max-height: 100%;
}

If only the .woosq-popup is set to a max-height of 100% it is not possible to scroll the overflowing part of the popup on a smartphone. Therefore input the following CSS as well:

@media only screen and (max-width: 768px) {
.woosq-product {
        overflow-y: scroll;
        height: 600px;
}
} 

Thanks, Bjarke

One CSS declaration was missing to make this work:

.woosq-product > .product > div {
    height: unset!important;
}

To be clear: All this must be written in your Themes custom CSS to make the popup 100% height AND work on a Smartphone:

.woosq-product > .product > div {
    height: unset!important;
}
.woosq-popup {
    max-height: 100%!important;
}
@media only screen and (max-width: 768px) {
.woosq-product {
    overflow-y: scroll;
    height: 600px;
}
}

Suggestion for updating the WooCommerce Quickview plugin:

How about making an additional setting where one can choose the height of the popup between a pixel-based height or a 100% height?