I concur, both options help a lot. I noticed that the ffmpeg packages are sometimes a bit outdated, yielding a gigantic gap between what the stock ffmpeg can do

I concur, both options help a lot. I noticed that the ffmpeg packages are sometimes a bit outdated, yielding a gigantic gap between what the stock ffmpeg can do, and what a freshly compiled one does. Also, having more cores helps a lot with SVT-AV1.