This is related to WebGL using the OpenGL ES 2.0 rendering backend - which has some hard-coded performance decisions which make sense for mobiles, but not so much for more performant desktop GPUs. WebGL 2.0 will fix this because it uses the GLES 3.0 rendering backend, but ultimately, we should change our shader code not to hard-code such decisions based on rendering APIs. This is something we want to do, but I have no idea when we will find time to do so.
Im not sure how those settings affect the performance or loading times but I was able to eliminate jagged shadows. Don’t ask me what setting solved this, I just played with random settings and this setup seems to work in every project.
