Hi again,

1. Header:
Sorry, I don’t understand your issue.

What header do you want to use? And what issue I can help you?

2. Custom Icon mega menu:
Our theme not support add new icon via svg folder.
To add new icon:
1. Import file font icon via Elementor
2. Edit Menu Mega Item, Select Custom Class ( Icon): https://prnt.sc/vg0qjw and add class icon to it.