For whiteboarding, I prefer Whimsical (whimical.co) over Figma or Mural. It's focused on digramming, wireframing, and mind-mapping; it's an absolute joy to use. Blazing fast, simple, and stays out of your way.
For context, I spend much of my day designing in Figma, which I love as well, but not for whiteboard-style collaboration.
- https://magicui.design/docs/components/border-beam - https://ui.shadcn.com/