Edited and partial copy-paste from reddit comment:

Sometimes VRR starts to jump around target refresh rate and depending on how bad these jumps get, monitor starts to flicker as addition to stutter-like behaviour.
For example a mild case may be a 60 fps video playing and vrr jumps between 57 to 63hz, which still ends up very mildly stuttering but monitor backlights don't flicker so it's not really bothersome. But there are cases when in same example, it jumps randomly to any refresh rate (60,50,63,165 e.g) resulting in heavy backlight flickering.

Gamescope's embedded mode doesn't suffer from this issue and refresh rates are so stable that I would say it's perfect. Maybe it works so well because gamescope bypasses XWayland?

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.0.3
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.3
Kernel Version: 6.8.4-1-clear (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5700X 8-Core Processor
Memory: 31,3 GiB of RAM
Graphics Processor: AMD Radeon RX 6800