How to replace post-upload text? Currently it shows filename and file size.

This is done via custom CSS. 

uploadcare-widget-file-name and uploadcare-widget-file-size are CSS classes that interest you. 

Suppose you want the widget to show text label "Edit" instead of default values. Following style sheet snippet will do that for you: 


.uploadcare-widget-file-name:before {
content: "Edit"; 
visibility:visible;

}

.uploadcare-widget-file-name {

visibility: hidden;

}
.uploadcare-widget-file-size:before {
content: ""; 
visibility:visible;

}

.uploadcare-widget-file-size {

visibility: hidden;

}