How does this compare to https://github.com/RazrFalcon/resvg ?

That's a different kind of thing, I think. It renders using tiny-skia, so probably comparing to tiny-skia would be more appropriate? It also sounds like resvg's renderer can be swapped out, so it may be possible to have it render with Forma.

That sounds neat.

I just tried it in my own renderer (that uses tiny-skia) to compare performance, but unfortunately forma is still lacking some features to do a proper comparison (strokes, the ability to scale shapes up instead of only down (?????), rendering without clearing).