since you up to date and there is no issue, so it was not related to kernel/nvidia but very likely to btrfs, which is still not stable enough …
now go to system settings/compositor and change the:
scale method to smooth
latency to force smoothest animations, click apply;
disable the indexer if you didnt do it yet;
then open this file:
kate /etc/environment
and add there this line:
QT_LOGGING_RULES='*=false'
save it - it will disable the kwin/qt logs
now open this file:
kate /etc/systemd/journald.conf
and edit this line:
#SystemMaxUse=
to look like this:
SystemMaxUse=25M
the ‘#’ at the beginning is removed
this will limit the journal/log size
save the file and restart journal:
systemctl restart systemd-journald