Things work better on LE due to the OS being overall lighter and because Kodi setup with adjust-refresh and whitelists etc. requires less compute resources during playback than a desktop app under wayland that's forced to resample audio and video to run at the desktop rate of 1080@60Hz or 4K@60Hz.
The buffer size issue is the main thing to focus on for VDPU346. The VP9 patches seem to work well and I'm coaching Abhi Sarma on kernel etiquette so hopefully a v1 series can be sent for review soon.
The minor tearing/glitches that can be seen when the Kodi OSD is active are the result of refactoring in the ffmpeg patches (dealing with ffmpeg developer feedback/requirements) and additional work in Kodi is needed to get back to the previous state where there were no artefacts. More patch series need to be merged down, then some effort can go into investigating that.