You posted details about an AV1 video; as written above, no HW decode is enabled for AV1, but your HW is powerful enough not to need HW video decoding, so I don’t think that is the key to the problem.
Your drivers look OK, as is your network apparently.
There was a similar problem reported recently, maybe in a similar configuration (KDE, dual boot W11, Nvidia drivers…). I don’t really know if it might be related, but please see spurious-interrupts-cauisng-system-stuttering and check if there are other similarities; maybe the video stuttering is just a KDE stuttering, just more likely when you are playing videos?
Other than that I see no obvious culprit, maybe other members with more experience with AMD HW can offer a better view.