This is a long thread, and I'm not sure how relevant this, but I'll just add this in from my own experiences:
Having a low framerate in webgl still produces smooth animations.
Having ANY framerate on a canvas produces jerky motion for me, even if it's at 60fps.
How I come to these conclusions:
WebGL enabled browsers on a variety of computers all run it smooth regardless of framerate
My systems without GPU acceleration don't have webgl (VMs and an old linux box) can't run webgl, and no matter what framerate C2 reports movement is very jerky, as if DT is either slighty off or greatly inconsistent (pixel rounding issue for non webgl canvas maybe??).
On mobile, chrome runs C2 games like a champ, but the system browser, again, has no webgl and while it reports 40+ fps, movement is very jerky.
(all movement is based on speed * dt)