Hello
Thank you so much for contacting us!
1- There is no such feature is available in this theme package, you can change dark or light mode by going to Dashboard > Theme Options > Syling & Colors https://prnt.sc/1r4tvdu
2- As for header setting is concerned we are sharing a video tutorial for your better understanding where you can easily get how to manage your header section accordingly. https://www.youtube.com/watch?v=RbdKjQrFnO4&list=PLMqMSqDgPNmDu3kYqh-SAsfUqutW3ohlG&index=3 ,
you can adjust the width by going to Dashboard > Theme Options > Header Builder > Main Header https://prnt.sc/1r4uy80
3 – You can change the icon by going to Dashboard > Appearance > Menus and then click on 8Theme Category Options https://prnt.sc/1r4v87e a popup window will open and change the icon according to your requirements. https://prnt.sc/1r4vc65
John Holden