Hello,
01. No, you don’t have to build them separately. In WoodMart Header Builder, there are “Desktop view” and “Mobile / Tablet view.”
You can use the same header for all devices and customize the mobile layout separately.
Please follow this guide on how it works: https://xtemos.com/docs-topic/woodmart-header-builder/
02. Could you please elaborate on your concern more with some useful highlighted screenshots so that we can better understand and assist you accordingly with what you actually want?
Best Regards,