Just wanted to make small update here, first in regards to the stuttering it seems to be problem with triple buffering and there was a merged MR to fix that, you can find additional information here: backends/drm: allow having two frames in flight ("triple buffering") (!4833) · Merge requests · Plasma / KWin · GitLab
As for the hangs/freezes, it turns out it wasn’t a freeze, but instead it just hangs the plasma panel/widgets/desktop/etc when you hide the panel, as long as you don’t hide panel or make it to dodge windows it’s fine, I have filed a bug report in regards to that here: 487728 – Plasma panel/widgets freeze randomly with explicit sync, can be unfreezed by going into overview
EDIT: Forgot to mention(though I’ve described it in the bug report) one way to workaround that issue with hidden panel causing freeze is to trigger the overview (super+w) and to close it again, that is as long as the panel is visible and not hidden.