Actually, the quick gallery is done the same way as the full list gallery tutorial here:
https://www.styledthemes.com/preference-theme-setup/70-create-a-list-gallery-with-spotlight-and-lightbox
When you put the list gallery code into a text widget, the theme is responsive, so when the thumbnails are in place, they will resize to fit the widget space. However, if you still run into any problems, let me know.
