Hi @AndrewsDesk and welcome to the community.
Yes you can change the scroll speed with the data attribute : data-scroll-time
See more here : https://discourse.webflow.com/t/customize-webflow-anchor-scrolling-behavior-speed/301/5
Yes you can have a fixed or sticky header, you can find more info here :
https://www.youtube.com/watch?v=5UlHsX1KDco
and here :
https://university.webflow.com/lesson/create-a-fixed-navbar