So I had installed the latest version of OBS Studio (26.x) from the official channels but when I went to the output mode it only listed software encoding. In the logs it mentioned FFMPEG-VAAPI but wasn’t using it as any recording was using 30%-50% CPU on a low powered laptop.

In Settings -> Output change Outmode to Advanced (from Simple) then on Streaming -> Encoder change that to FFMPEG VAAPI (Recoding should just be set to use Streaming Encoder which is the default)

But then when I tried to record it

[FFMPEG VAAPI encoder] Failed to open VAAPI codec: Invalid argument

To fix this I then had to set an environment variable on start

 LIBVA_DRIVER_NAME=i965 obs

To change the shortcut for OBS I did the following

cp /usr/share/applications/com.obsproject.Studio.desktop ~/.local/share/applications/

nano ~/.local/share/applications/com.obsproject.Studio.desktop

Change the Exec line as follows

Exec=env LIBVA_DRIVER_NAME=i965 obs

Now recording only uses 5-10% CPU on the same laptop