You might be running into the issue of your SnapWidget looking perfect in your editor, but not in your preview or live site.
To adjust the size and display of your Instagram widget:
First, click the IG widget to select it, then you will need to click into the embed code for the widget under the embed code tab in the Properties Panel.
(for larger image: Right Click>Open Image in New Tab)
For the height & width, change that value to 100% and then click save.
Then publish or preview! Your Instagram widget should be sized just like it is in the preview.