I have used x265 fairly easily to encode a 4K Bluray. None of the AV1 options seem to have the required performance (both quality and encoding speed) and ease of use.
SVT-AV1 has been both faster and higher quality than x265 for awhile now though? For ease of use, you can just use ffmpeg, or one of the many CLIs or GUIs that support AV1 (preferably either Av1an for CLI, or a gui that uses it under the hood eg. nmkoder).
This is false, relative to x265, there is some preset which provides both faster encoding and higher "quality", iso-bitrate, across the whole gamut of x265 settings, and I believe x264 as well, although I am not entirely sure about what is available at the extreme inefficient/fast end (the usefulness of which is questionable).
Also dav1d
libaom https://aomedia.googlesource.com/aom, the reference implementation.
https://gitlab.com/AOMediaCodec/SVT-AV1 - from the Alliance for Open Media, which Intel is deeply involved with and is spending a lot of time optimising.
https://github.com/xiph/rav1e - written in rust, also subject to a lot of optimising. It's not complete coverage of all features, intended to be used for places where libaom is too slow.