With regard to WebGL, it depends. This demo, for example, runs at 30fps in Firefox for Android and 4fps in Chrome on my Nextbit Robin: https://www.shadertoy.com/view/Ms2SD1
Shadertoy is just drawing a plane with a shader. Many less graphics calls than a regular WebGL app (which is where Chromium still shines). Even then, Chromium renders that link full screen a bit smoother than FF in Linux desktop.
