I need to test epiphany without hardware acceleration to see if it is the culprit for the graphical glitches I'm experiencing in epiphany. Is this possible? It doesn't appear in the main setting menu. Maybe in a hidden menu similar to Firefox's about:config?
This is possible by setting an environment variable. Run it from the terminal like this:
$ WEBKIT_DISABLE_COMPOSITING_MODE=1 epiphany
See https://trac.webkit.org/wiki/EnvironmentVariables for other environment variables that you'll probably never want to use.
If this environment variable fixes your problem, then there's a good chance it's a bug in your hardware or graphics driver, but there's an equally-good chance it's a bug in WebKit. Regardless, your best hope of getting help is to report the issue on https://bugs.webkit.org.