Author here. I'm sorry that it performs poorly on your machine - if it makes any difference, it's the rendering that is slow, not the layout.
The HTML examples are more meant as a demo than anything else, as the library actually doesn't do any rendering itself at all, it's exclusively a layout tool.
I'm honestly not sure why the performance differs significantly between machines - I'm on an M1 mbp / firefox and it scrolls at 120 fps for me.