i THINK the wiki is outdated, but im not sure.
When i installed arch a couple of months ago it seemed to work out of the box as well(with a dedicated gpu).
As for the jitter in firefox, i have had the same problem on fedora kde(which i'm currently dailying), which happened only recently.
I think its a bug in firefox, and while reinstalling arch and updating the system, a new update for firefox that fixed the issue also got installed.
i THINK the wiki is outdated, but im not sure. When i installed arch a couple of months ago it seemed to work out of the box as well(with a dedicated gpu).
As for the jitter in firefox, i have had the same problem on fedora kde(which i'm currently dailying), which happened only recently. I think its a bug in firefox, and while reinstalling arch and updating the system, a new update for firefox that fixed the issue also got installed.