Professionals don't use OBS or VP9
For any codecs other than the default H.264 and AAC you have to use use ffmpeg output.
If you set the container to WebM it will default to libvpx-vp9 and libopus. Good luck!
Failed to open audio codec: Invalid argument
Ah yes, I tried it myself. You're right. The log shows this:
The included ffmpeg library is probably not compiled with --enable-libopus (I assume that's it)
You have to check the box that says "Show all codecs (even if potentially incompatible)"
And select libvorbis as your audio codec.
I tried it just now. VP9 + Vorbis. Works fine :)
It's true that it's CPU heavy but I don't use OBS for recording of games and only record in 25fps for some projects. My PC should be able to handle it with an Ryzen 7 3800X.I have seen a other forum saying that VP9 is CPU intensive and cannot be used in realtime encoding, I'm not sure but crashes on mine i5-8265U too.