Can I change how fast the curtain scrolls?
Short answer: Yes. In Settings → Advanced → Junk Yard Edge Curtain there's a Scroll speed slider for edge auto-scroll, pointer movement, and trackpad/scroll-wheel, from slow up to 5× fast.
Yes. Settings → Advanced → Junk Yard Edge Curtain has a Scroll speed slider for each of the curtain's three ways of scrolling: edge auto-scroll, pointer movement, and trackpad and scroll-wheel. Each runs from slow up to 5× fast.
At its default, trackpad and scroll-wheel scrolling keeps the Mac's natural momentum and bounce. Reset to defaults restores all of them.