Aha, looks like the issue is not graphics slowness, but a side effect of the way that Make Text Layer renders sharp text.
Make Text Layer snaps the text to pixels so that it's totally sharp rather than blurred across pixels. However, as your composition points out, this can interact weirdly with scrolling text across the window. To keep the text sharp, Make Text Layer causes the text to jump from one pixel to the next. Depending on how the scrolling events line up in time with pixels in space, the text could actually move 1px or 2px or 0px on a given display refresh. Hence the jerky motion.
If you remove Make Text Layer and just use Make Text Image — which, when combined with Make Image Layer non-realsize, does not snap to pixels — that should be smoother. With the attached composition, if you slow down the scrollers and zoom in, you can see the pixels gradually fade in and out as it moves along.
The Logitech C920 only provides 30fps at 1080p with applications that supports H.264 directly, and can pull in the H.264 stream directly from the camera. The C920 does on-board H.264 compression, but most applications don't support pulling the compressed stream straight from the camera; instead, they have to decompress then re-compress the stream, dropping the framerate.
Does that sound right? Does VUO support H.264 camera streams?