I'm a big fan of Excalidraw! And a contributor, too, I implemented the pen tool in Excalidraw. Both apps use my library perfect-freehand (https://github.com/steveruizok/perfect-freehand) for the digital ink.
The main difference between the two is that Excalidraw renders to HTML canvas, while tldraw renders to a regular DOM tree. There are tradeoffs but this lets us make things like sticky notes or other types of complex embedded content without too much difficulty.
