https://modding-openmw.com/tips/perform ... cific-tips
If you're using a modern AMD GPU on a modern Linux system (e.g., I've got a Polaris 10 card on a rolling release distro), it might be a good idea to try running OpenMW with the OSG_VERTEX_BUFFER_HINT=VERTEX_BUFFER_OBJECT environment variable. On my own setup, this doubled my average FPS with very high settings.
This is known to not make any difference with Nvidia GPUs (and may have a negative impact on performance), but it is unknown to me if it makes a difference with AMD GPUs on Windows.
In Mint, I just set this up as a global setting via a compositor menu setting. In Manjaro - I never found the option - but OpenMW's Application Launcher can be edited like so:
On my modest system this gives me at least a 5-8 FPS gain.