@Jeff:
1. Fixed header height changes, if you change the height of menu items or logo or icon as it is wrapped by menu wrapper. We called that as Fixed header top menu. But if you like to manually increase the height, then you can adjust the height in the following css as per your need and then add it in “Appearance => Customize => Theme Options => Custom CSS Options” box:
.nav-primary { height: 50px; }
2. To change the number of Featured Content. You need to go to “Appearance => Customize => Featured Content => Featured Content Options => No of Featured Content” and change the number and click on “Save & Publish”, then you need to refresh your browser or close the customizer and reopen it again as that customizer need to be refreshed. Then you will see the number has been changed.